Answer:
221/9
Step-by-step explanation:
3+ sqrt( 9x + 4) = 18
Subtract 2 from each side
3-3+ sqrt( 9x + 4) = 18-3
sqrt( 9x + 4) = 15
Square each side
(sqrt(9x+4))^2 = 15^2
9x+4 = 225
Subtract 4 from each side
9x = 225-4
9x = 221
Divide by 9
x = 221/9