So the equation,in text form, is 8*cbrt[x + 3] = 11 or, in LaTeX formatting:

. . . . .

A good first step insolving this radical equationwould be to get the radical by itself, so start by dividing through by 8.

Then cube both sides to get:

. . . . .

Subtract the 3 to the right-hand side, and simplify.

By the way, whoever told you that the solution is "x = 4" was mistaken. That's why, when you plugged "4" in for "x" on the left-hand side, you didnotget a value of 11.