x = 30
From the equation;
x(x-5) =750
x² -5x =750
forming a quadratic equation;
x²-5x-750 = 0
but; 30, and 25, are numbers you can multiply to get 750 and have a difference of 5
Therefore;
x²-30x + 25x -750 = 0
x(x-30) +25(x-30) = 0
(x+25)(x-30) = 0
Therefore; x = -25 or x = 30
Thus the value of x = 30