The equation is y=m(x)+b
So to find b you have to plug in the numbers y=-2 x=3 the slope aka 13 is m.
-2=13(3)+b
Now you are trying to get B by it’s self. So you do 13x3=39. Then do -2-39= -37
B= -37
So the answer is y=13x+ -37
Which will simplify down to y=13x-37