Hey!
Please check if you have given all the information for this problem. If they have given you another point on the line, you will need to use that to find the y-intercept. The slope of both the lines will be the same, 10, because they are parallel. You can then plug in the x and y into this equation along with the slope m:
y = mx + b
y = 10x + b
You are trying to find b.
