Solve each system with substitution.

Question

-4x + y =6

-5x - y =21

Please help us understand this for an 8th grade algebra class.

Answer 1

This system will be solved more easily with elimination, but since substitution is required, here is the m

In the first equation, add 4x to east side to get: y = 4x + 6

Use this value of y to substitute into the 2nd equation:

-5x - 4x - 6 = 21

Add 6 to each side and collect terms:

-9x = 27

Divide by -9

x = -3

Then go back to the expression for y = 4(-3) + 6 = -6