Square both sides:
15x + 18 = 25x²
25x² − 15x − 18 = 0
25x² − 30x + 15x − 18 = 0
5x (5x − 6) + 3 (5x − 6) = 0
(5x − 6) (5x + 3) = 0
x = 6/5, x = −3/5
Check for extreneous solutions that may have been introduced when squaring
x = 6/5
√(15x+18) = √(15(6/5)+18) = √36 = 6
5x = 5(6/5) = 6
x = −3/5
√(15x+18) = √(15(−3/5)+18) = √9 = 3
5x = 5(−3/5) = −3
The only solution is: x = 6/5
