What you need to do is change the equation to the form y=mx+b.
So,
[tex]5y=10x-15[/tex] Add 10x to both sides to move 10x from the right side.
[tex]y=2x-3[/tex] Divide the 5 from 5y to isolate the variable.
Now, the equation is in y=mx+b, and the slope of the line is m, so the slope of this equation is 2.