Grant would swim three the middles of the pool (just doing this for the points)

There are no such numbers in real numbers.
Do you perhaps want a solution in complex numbers?
Well 9x40 would be the solution, so what is 9x40? That will be your answer.
5-3 is 2 multiply that by 3 and you get 6 add that to 53 and you get 59... using PEMDAS
Answer:
for (8,4) is 2 and for (20,_4) is _5