CPhill

Let x be the smaller angle....and we have that...

x + (7x + 4)  = 180   simplify

8x + 4  =  180     subtract 4 from both sides

8x = 176    divide both sides by 8

x = 22°  = the smaller angle

7(22°) + 4   =  158°  = the larger angle

5 + 1/2 ft =   66 inches

So

66/ (3/4)   =   66* (4 /3 )   = 66/3 * 4  =  22 * 4 =   88 books  can actually fit

I think the problem is "the years past 2006"....if we use 2006 as "year 0,"   then 2011 will be "year 5"  .....and we have the points  (0,85) (5,88)    ....the slope  is given by :

[ 88 - 85 ] / [5 -0]  =   3/5

And using either point - I'll use the first one - the equation  becomes

y - 85  = (3/5) (x - 0 )

y = (3/5)x + 85

This equation is correct....note that putting in "5" for x gives us 88

So.... in 2020, x will  = 14 and we have

y = (3/5)(14) + 85  = 93.4 persons per square mile

if 3t - 7 = 5t then 6t = what?

3t - 7  = 5t         subtract 3t from both sides

-7  = 2t           divide both sides by 2

-7/2  =  t   = -7/2

So...6t =   6(-7/2)  = -42 / 2    = -21

x^2 - 64    =

(x + 8) (x - 8)

4.21x + 5.39 = 12.07(2.01 - 4.72x)     multipy through by 100 to help clear some decimals

421x + 539  = 1207 (2.01 - 4.72x)        simplify the right side

421x + 539  = 2426.07 - 5697.04x    add 5697.04 to both sides, subtract 539 from both sides

6118.04 x =  1887.07        divide both sides by 6118.04

x = 1887.07 / 6118.04  

8 times 100 plus  3 times 1/10 plus 6 times 1/100

 [8 * 100 ]  + [ 3 * (1/10)]   +  [ 6 * (1/100)]  =

800 + 3/10  + 6/100  =

800.36

3(1/3) + (-7/4)  =

1  - 7/4   =

4/4  - 7/4  =

-3/4

3(13) + (-7/4)  =

39  - 7/4   =

156/4 - 7/4  = 

[156 - 7]  / 4  =

149/4

 x+3y-3z=-12      (1)

3x-3y-4z=14       (2)

-5x+4y+5z=-15    (3)

Add (1)  and (2)

4x - 7z   = 2     (4)

Multiply (1) by 4   and (3)  by -3....this gives us

4x + 12y - 12z = -48

15x - 12y - 15z = 45        add these giving us

19x - 27z   = -3     (5)      multiplly (4) by 19   and (5)  by -4   ....this gives us.....

76x - 133z = 38

-76x + 108z = 12        add these

-25z   = 50       divide both sides by -25

z =  - 2    and using (4)  to find x, we have  that  4x - 7(-2)  = 2  →    4x + 14  = 2   →  4x = -12 →   x = -3

And using (1) to find y, we have :  -3 +3y-3(-2)=-12 →   3 + 3y  = -12   →  3y = -15  →  y  = -5