Question

What is the x value such that y=15-3x and y=0

Answer 1

X=5

because 15-3(5)=15

So, 15-15=0

X=5

Answer 2

y=15-3x substitute 0 for y
(0)=15-3x subtract 15 from both sides
-15=-3x divide by -3 on both sides, a negative divided by or times by another negative will always equal a positive so x equals positive 5
x=5