The equation of the line that is parallel will have the SAME slope as the given equation. So m = -1/5.
You use the equation y = mx + b
SInce you know m you can plug it in.
y = -1/5x + b
Now you need to find b. To do so you plug in the point (1,2) into the equation.
2 = -1/5(1) + b
2 = -1/5 + b
2 + 1/5 = b
10/5 + 1/5 = b
11/5 = b
Your equation is:
y = -1/5b + 11/5