Since we know the lines are parallel they must have the same slope. That is the first place to start. We know that the slope intercept form of a line is y=mx+b where m is the slope and b is the y itnercept
Since we know the slope or m value we can start by writing this as
y=-5/2x+b
now we need to find the y intercept or b value.
The easiest way to do this is to graph the line by plotting the point and using the slope to find other points. Here is a graph of the two lines:
The y intercept of the unknown line, or the point at which it crosses the y axis is 23. The equation then for the unknown line is
y=-5/2x+23