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Explanation:
Solve each equation for y. In other words, get y by itself
Let's start with the first equation
-3x = 3 - y
-3x - 3 = -y
-y = -3x-3
y = 3x+3
Do the same for the second equation
-1+y = 3x-2
y = 3x-2+1
y = 3x-1
The two equations we got were
y = 3x+3
y = 3x-1
Both have the same slope (m = 3) but different y intercepts, so we have parallel lines here.