Starting equation: ( 4
9
) x+1 = ( 27
8
) x + 6
Re-write   ( 4
9
) = ( 2
3
) 2 and ( 27
8
) = ( 2
3
) -3
The above two revisions result in this equation:

[( 2
3
) 2 ] x+1 = [( 2
3
) -3 ] x + 6
and using Rules for exponents:
( 2
3
) 2(x+1) = ( 2
3
) -3(x + 6)
If the powers are equal, and the bases (here, 3) are equal then the exponents must also be equal:
2(x + 1) = -3(x + 6)
2x+2 = -3x - 18
5x = -20
x = -4