Since the line is perpendicular to y=5/3x-5, We can find the gradient since perpendicular lines have negative reciprocal gradients of each other, so in this case the gradient of the line is -3/5. We have a point, we have the gradient, so we can substitute in y=mx+c to find the y-intercept c, so -5 = (-3/5)(-7) + c.
