log (x+5)+log (x+29)=4
3 3

the 3's are subscripts to log

2. $\log_3 (x+5)+\log_3 (x+29)=4$

Consider

$\log_ab+\log_ac=\log_a(b\times c)$

So

$\log_3 ((x+5)(x+29))=4$

Raise both sides to the power of 3 gives

$(x+5)(x+29)=3^4$

now you have to solve the quadratic. All good?