Which of the following represents "the square of the sum of a number and 4 is 36"?

Lets write the information as an equation, and name x the number unknown:

(x + 4) ^2 = 36

that is:

the sum of a number and 4: (x + 4)

then, the square of the sum of a number and 4: (x + 4) ^2

so we have:

(x + 4) ^2 = 36

to solve we calculate square root to both sides of the equation:

(x + 4) = 6

then we solve for x:

x = 6 - 4

x = 2

so the unknown number is 2