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x ( .04)     + (15 000 - x) (.05)    = 690       solve for x  (the amount at 4%)     then the 5% amount is 15 000 - x

If you must have two variables

x = 4% amount

y = 5% amount  

x + y = 15000            y =   (15000 - x)

.04 x   +  .05 y = 690             now  y = 15 000 - x    sub that in

.04x   + .05 ( 15000 - x) = 690

3n   = money fron 'n' raffle tix

3n  > =.07n  + 45

n >= 15.35                              they must sell at least 16 tix to make money

[WXYZ] = 18 √50

 2 - 2 - 6 triangle does not work, because 2 + 2 is less than 6.

Thus, the only working options are 3 - 3 - 4 and 2 - 4- 4, making \(\color{brown}\boxed{2}\) options. 

2-2-6

2-4-4

3-3-4

(10²⁰)² - 2·10²⁰ + (-1)²                    Slight correction ......

10⁴⁰ - 2 * 10²⁰  +1  

Smallest integer > sqrt (690)                   sqrt 690 = 26.3

Smallest integer > sqrt 690  is then 27

Not sure what you mean by this part : 690−−√690

         690 -   - sqrt 690

          = 690 + sqrt 690

           =   690  + 26.3   = 716.3               then the answer would be   717   

If 64 cm is the circumference of A     then B AREA = 64/4 = 16 cm²

Area =   pi * r^2

     16               =   pi  r^2

     16 / pi =    r^2 

          r  = 2.2568 cm

Also please show my step by step don't just give me an answer

I don't know your level; I'm going to assume you are somewhere in the grade 5 to grade 9 range.

First, know the arithmetic facts; algebra will be just doing basic arithmetic but using letters (variables)

instead of numbers.

Know the addition table; do not use quick counting (on your fingers) instead of having the table

memorized.

Also, know the multiplication table; quick adding (on your fingers) won't be enough -- memorize!

[You've memorized the states and their capitals; you can also memorize arithmetic tables!]

Studying with someone can be a great benefit; talking through problems with someone else can really

help you understand the material. Study with someone who really wants to learn, not just get an

answer and go on. If you can find someone to study with, math can become fun and not just work.

With someone else, you will be able to greatly increase your understanding; and, once you understand

math, it will no longer be a mystery and a chore.

If you have had trouble with fractions, you will need to start over with fractions and learn how to work

with them. The same with percentages. 

Starting over with areas that you've had trouble with in the past won't be fun, but can really help you

out in the future. Several occupations require math ability; without this ability these areas may be 

closed to your. Working now may really allow better things for your future! It's hard, but worth it!

Question:  What is (10²⁰ - 1) x (10²⁰​ - 1) ?

This is a binomial, so it can be simplified as:

                    =  (10²⁰)² - 2·10² + (-1)²

                    =  10⁴⁰ -  2·10² + 1

And, if you are really interested, you can finish this ...

Density =   mass / volume

              = (105.25 - 82.14) / 25 = _________  gm / ml

The red part is the mass of the liquid

Let C  = area of smallest circle

Let B = area of next largest circle

Let A = area of largest circle

Shaded area =  B - C

Unshaded area = C + ( A - B)

C /  A =  2 / 5    ⇒    A  =  (5/2)C

Shaded Area / Unshaded Area =   

(B - C)  / [ C + A - B ]  =  3/ 7

( B - C )  / [ C + (5/2)C -  B ]  =    3/7

(B - C) / [ (7/2)C - B ]   = 3/7

3 [(7/2)C - B ]  = 7 (B - C)

(21/2)C - 3B  =  7B - 7C

(21/2)C + 7C  =  7B + 3B

(35/2)C = 10B

(35/20) C  = B

(7/4)C = B

C = (4/7)B

Unshaded Area / Smallest circle

(B - C)  / C  =  [ (B - 4/7)B ]  / [ (4/7)B ]   =  (3/7B) / [ 4/7) B =   3 / 4  [ As Melody found !!!  ]

1   5    17   53    161     485    1457   4373         eight terms     ( none are multiple of 4)

3 times any number   + 2     is never a multiple of 4

1- 9      9 digits

91 digits left

   or 45   two digit numbers PLUS 1 more digit

      10 - 54    is   45 two digit numbers    the next digit you write would be   5     ( the first 5 in 55)

Please don't post questions more than once ....    see other post