Use PEMDAS to evaluate the operations from left to right in proper order: Parentheses, Exponents, Multiplication/Division, Addition/Subtraction.
This is easily remembered by: Please Excuse My Dear Aunt Sally.
For this problem, the process would look like this:
\[5 + 4 \cdot 3 \div 2 - 8\]
\[5 + 12 \div 2 - 8\]
\[5 + 6 - 8\]
\[11 - 8 = 3\]