The priority of the operators follows the usual conventions:

The highest priority is assigned to unary operators (note that, in this context, a function such as sin is considered a unary operator). All unary operators have the same priority.

Exponentiation has the second highest priority.

The third highest priority is assigned to the multiplication and division operators.

The lowest priority is given to the addition and subtraction operators.
Example:>>
Infix expression: $3 * \log( 10 )$
Postfix expression:
$=3 * (10 \log)$ //(Priority of unary operator log forces $\log( 10 )$ to evaluate first.)
$=3 \ 10 \log *$
Now for our case $3*\log(x + 1)  a / 2$
First content inside parenthesis will be evaluated
So, $x+1$ will become $x\;1+$
Now among $(*,/,\log,+,)$ operators, $\log$ has highest priority as it is the only unary operator
So, $\log(x\;1+)$ will become ${x\;1+\log}$
Now suppose ${z= x1+\log}$ and we get $3* z  a / 2$
$\implies 3z* a\;2/ $
Now, substitute $z= x\;1+\log$ and we get
$\mathbf{3x\;1+\log* a\;2/ }$ as answer.