Question:

If the square of a whole number is decreased by 9 times the number, then the result is 36. Find the number.

Answer:

B. 12

Step-by-step explanation:

x² - 9x = 36

x² - 9x - 36 = 36 - 36

x² - 9x - 36 = 0

( x + 3 ) ( x - 12 ) = 0

x + 3 = 0 or x - 12 = 0

x = -3 or x = 12