how to solve diz type of questions

Let x stand for the "mystery number" you are trying to find.

75% of x plus 75 = x

0.75x + 75 = x

Bring the variable terms to the left side of the equation by subtracting x from both sides.

-0.25x + 75 = 0

Bring the constant terms to the right side by subtracting 75 from both sides.

-0.25x = -75

Divide both sides by -0.25

x = 300