ElectricPavlov

1/20  + 1/15  + 1/12  = 1/x     solve for 'x'   the time requird for all 3

You should post each Q seperately with their own header.......but here is this one

M/L = 2/3

A.    4/L = 2/3   solve for L = 6 mi

B.   M/930 = 2/3    solve for M = 620 m

C.   4 : 6      620: 930    are equiv to  2:3

https://web2.0calc.com/questions/pre-calculus_20

amountleft = amount (1-.5)ⁿ        Where n = number of half lifes     amount left = 1 - .76 = .24

.24 = (1-.5)ⁿ

.24 = .5ⁿ        Log both sides

log .24 = n log .5

log .24 / log .5 =  n

n = 2.0589 half lifes = 61.77 seconds 

*** deleted ***       problem with server caused multiple postings of the same things

I think this?

9^x  + 3^1+2x  = 50

3^2x  + 3^1+2x

3^2x +3 * 3^2x

4* 3^2x  = 50

3^2x  = 50/4 = 12.5   take logs of both sides

2x log 3 = log 12.5

2x = log12.5/log3

x = 1.1495

Let's see how long it wil take them to build THREE walls....then divide the resulting time by 3

1/6  + 1/9  + 1/12  =  3/x

(12 + 8 + 6) / 72  = 3/x

26/72 = 3/x

x = 3 * 72/26    x = 8.30769   for THREE walls  

One wall = 2.7692 days

Your equation is still a bit of a mess.....

You need to proof read your equation .......

5.57%   =  .0575

quarterly interest =  .0575/4 = .014375

due at the end of 'n' years would be (put the number of years for 'n' and compute):

         5000 (1 + .014375)⁴ⁿ