Question

To solve this system by substitution, which variable in which equation should be isolated?

{(4x+5y=4),(2x+y=7):}
x in the first equation
y in the first equation
x in the second equation
y in the second equation

Answer 1

I would go for y in the first equation

Explanation:

1. Eliminating x and isolating y is easier
   4x + 5y = 4;
   2x + y = 7;
2. Multiply both sides and eliminate x
   4x + 5y = 4;
   -2(2x + y) = -2(7)
   -4x -2y = -14;
3. Combine the equations
   4x - 4x + 5y - 2y = 4 - 14
   3y = - 10
   y = (-10/3)

You get y from the first equation I guess. The question is a bit confusing though.

Answer 2

X is the first variable to use for this equation