Simple....
you have:
(-15,70) and (5,10)
Using-->>
[tex] \frac{ y_{1} -y_{2} }{ x_{1}- x_{2} } [/tex]
[tex] \frac{70-10}{-15-5} = \frac{60}{-20} = -3 [/tex]
Using y=mx+b...and any of the coordinates....
70= -3(-15)+b
70=45+b
70=45+b
-45 -45
25=b
y=-3x+25
Thus,your answer.
