Solve for x.

2 log (x + 1) = 3

log (x+1)^2 = 3

(x+1)^2 = 10^3
x+1 = ± √1000
x = √1000 - 1 or x = -√1000 - 1
but the second answer would make the log expression undefined, so

x = √1000 - 1 or appr. 30.6228