Question 78737
you can make this quite simple by cross multiplying:

set up the problem so that the numerator of one side times the denominator of the other side equals the other numerator times the other denominator.

Example:

d*d = (d+4) (d-2)
d^2 =  d^2 +4d -2d -8

subtract the d^2 from both sides, add up the 4d and -2d and bring it to the other side.

you'll end up with 2d = 8
divide by 2 to both sides
d = 4