On a scale drawing of a swimming pool, 1 inch equals 4 feet. the actual dimensions of the swimming pool are 15 feet by 30 feet. what are the dimensions of the swimming pool in the scale drawing? explain your answer.

We are dealing with a scale drawing, so the measurements of the actual pool and that of the drawing are directly proportional.
If 1 inch on the drawing equals to 4 feet in real life, then the scale factor from sale drawing to the actual dimensions is ×4.
However we need the scale factor from the actual dimensions to those on the scale drawing. This value will be the reciprocal (1 over a given number) of the small to large scale factor, so is ×1/4, a.k.a a quarter.
Now we can find the scale drawing dimensions of the swimming pool by doing:

(and don't forget to use inches as the measurement for the scale drawing):

So 15 feet = 3.65 inches

And 30 feet = 7.5 inches.

So the first thing we do is to multiply the top equation by 3. the reason i want to do this is i notice there will be a 6y on both equations and can possibly add/subtract them. so we get 6y = -3x + 27. adding that and the second equation we get 6x = 27-15 which is 12. divide by 6 and we get 2. ∴ x = 2. substituting 2 into the first equation we get 2y = -2 + 9 which is 7. divide by 2 and we get 7/2. ∴ y = 7/2, x = 2.