Question

What is the answer to y=6+4x and y=-5x-21

Answer 1

y=6+4x

y=-5x-21

=> 6+4x=-5x-21

9x=-27

x=-3

y=6+4*(-3)=6-12=-6

y=-6

Solution: (-3; -6)

Answer 2

y=4x+6
y=-5x-21

4x+6=-5x-21
add both sides by 5x
also subtract both sides by 6
9x=-27
x=-3

plu x=-3 in y=6+4x
y=6-12
y=-6