Question 527452
Let our answer be in the form 10x + y. We'll use this later.

x-y = 4  -->  x = 4+y 
xy = 45

(4+y)y = 45

4y + y^2 = 45

y^2 + 4y -45 = 0

(y+9)(y-5) = 0

This gives us answers of y=-9 and y=5. Since a negative answer won't give us the answer we're looking for, then y = 5 is the only logical solution.

Plug y = 5 back into either equation.

x(5) = 45

5x = 45

x = 9

Going back to our 10x+y...

10(9) + 5  = 95
Thus our answer is  95.