It's asking which equation you would use to isolate a variable. Explain your reasoning. Problem: x=8y-3 3x-4y=1

Question

It's asking which equation you would use to isolate a variable. Explain your reasoning. Problem: x=8y-3                 3x-4y=1

anonymous · Answer

The equation already has X solved for you, so plugging X from eq.1 to eq2 yields 3(8y-3)-4y =1. 
Distribute. 24y-9-4y=1. 
Isolate Y. 20y=10, Y = 10/20 = .5
You can then plugin Y in the other equation to solve for X.
x = 8(.5)-3
x = 4-3
x = 1

anonymous · Answer

okay. And i need help on another problem. Its asking to solve the linear system by using substitution. -x+2y=-6                     8x+y=31

anonymous · Answer

Like the other problem, you want to isolate a variable.

x is easier to isolate again in eq1.
x - 2y + 6

substitution into eq2.

8(2y+6) + y = 31

16y + 48 + y = 31

17y = -17
y = -1

Plugin Y into eq. 1 to get X.

X - (2*-1) + 6 = -4

y = -1
x = 4