Question

y = -x + 2;
7x + 4y = -1

Answer 1

y = -x + 2 --- now sub -x + 2 in for y in the other equation

7x + 4y = -1
7x + 4(-x + 2) = -1 --- distribute through the parenthesis
7x - 4x + 8 = -1 --- subtract 8 from both sides
7x - 4x = -1 - 8 -- combine like terms
3x = - 9 -- divide both sides by 3
x = -3
now sub -3 in for x in either equation to find y
y = -x + 2
y = - (-3) + 2
y = 3 + 2
y = 5

check..
7x + 4y = -1
7(-3) + 4(5) = -1
-21 + 20 = -1
-1 = -1 (correct)

x = -3 and y = 5