To solve the equation √x + 4 = 15, we need to isolate the variable x.

First, subtract 4 from both sides of the equation:

√x = 15 - 4
√x = 11

Next, square both sides of the equation to eliminate the square root:

(√x)^2 = 11^2
x = 121

Therefore, the solution to the equation √x + 4 = 15 is x = 121.