To find where the lines intersect, solve thesystem of equationsthat they represent.

Since they're already both solved for "y=", I'd use substitution. So set it up like so:

. . . . .

. . . . .

...and so forth. This will give you the point of intersection.

You are already given the slope (or gradient): . Plug this information into whicheverstraight-line equationyou prefer. Since you have a point and a slope, you might want to start with the point-slope form:

. . . . .

Multiply the slope through the parentheses, and then solve for "y=". The result is the equation you need.

If you get stuck, please reply showing how far you have gotten in working through the steps. Thank you!