Answer: 12
Explanation:
1) Create an equation. Lets call the missing number x. 36 is added to x or 36+x and when 36 is added to x it is 4 times of x or 4x, so our equation is 36+x=4x.
2) Bring the variable to one side by subtracting x on both sides. Our new equation is 36=3x.
36) Get rid off the coefficient 3 by dividing 3 on both sides to get x=12