so
perpendicular lines have slope that multiply to -1
y=mx+b
m=sloe
given
y=3/5x+10
slope is 3/5
perpendicular
3/5 times what=-1?
times both sides by 5/3
what=-5/3
the other slope is -5/3
y=-5/3x+b
find b which is the y intercept
passes through (15,-5)
input that (x,y) so x=15 and y=-5 is a point
-5=(-5/3)(15)+b
-5=-25+b
20=b
the y intercept is 20