the legs of a right triangle measure 3x and 15.if the hypotense measure 3x+3,what is the value for x

Using the Pythagorean Theorem, we have

15^2 +(3x)^2  = (3x + 3)^2    expand

225 + 9x^2 = 9x^2 + 18x + 9   rearrange and simplify

18x - 216 = 0

18x = 216

x = 12