E.
You are given two equations:
X/y = 24
X + y = 75.
You want to isolate the variable in one equation so you can plug it into the other one.
X/y = 24 can be simplified as x = 24y. (Multiply both sides by y to remove it from the denominator.) Plug the new equation into the other equation.
24y + y = 75.
25y = 75.
Y = 3
Now that you know y is equal to 3, you can plus it into one of the equations to solve for x.
X + 3 = 75
X = 72, therefore the answer is E.
