12x – 5y = -20
y = x +4

x = , y = -1.71

Step-by-step explanation:

sub y = x+4 in the first equation to get:

12 x - 5 (x+4) = -20

Simplify:

12 x - 5 x + 20 = -20

Further simplify:

7 x = - 40

Divie both sides by 7 to get:

x =

--> x = -5.7

Sub x =  in the second equation to get:

y =  + 4  = -1.71

(f - g)(x) = 5x^3 - 3

step-by-step explanation:

rearrange these functions vertically, with like terms in separate columns:

f(x) = 5x^3 - 2

g(x) =         +1

now subtract, column by column:

(f - g)(x) = 5x^3 - 3

you didn't post any answer choices, so its not 100% clear what your teacher is looking for

however, log(15/7) is equivalent to log(15) - log(7)

i'm using the rule log(x/y) = log(x) - log(y)