Answer
$-5\textbf {i}+41\textbf {j}$
Work Step by Step
Step 1: $3\textbf {U}+5\textbf {V}$
Step 2: $3(5\textbf {i}+12\textbf {j})+5(-4\textbf {i}+\textbf {j})$
Step 3: $15\textbf {i}+36\textbf {j}-20\textbf {i}+5\textbf {j}$
Step 4: $15\textbf {i}-20\textbf {i}+5\textbf {j}+36\textbf {j}$
Step 5: $-5\textbf {i}+41\textbf {j}$