Answer:
boom
Step-by-step explanation:
Since you have y alone on one side of the equation......
Use substitution and plug in 1/2x-4 for y in the other equation.

Distribute

Combine like terms

Add 8 to both sides

Divide by 4
and 
Plug this value in for x

Simplify

Multiply everything by 8 and simplify

Divide.....

Your answers are:

I had that question yesterday
I hope this helps you
125-87,5=37,5
125 37,5
100 ?
?.125=100.37,5
?=3750/125
?=30
30%
X^2-5x+5x-25 (multiply (x-5) with (x+5))
X^2-25 ( -5x+5x =0)