How do you solve a recurrence relation with multiple subproblems of different sizes? For instance, consider the following recurrence relation.


  T(n) = T(n/2) + T(n/3) + T(n/4) + n


Would you use the substitution method for this?
You can find an upper bound like this:
$T(n)\leq 3T(n/2)+n$.

Solving using master theorem,
$T(n)=O(n^{log_23})$