Use PEMDAS
PEMDAS stands for: Parenthesis, Exponents, Multiplication, Division, Addition, and Subtraction.
So.. in 7+5x6, you first multiply (Tip: If you don't see parenthesis or exponents, jump to multiplication) 5 and 6. (30) NOw, you add 5x6 (30) with 7 (=37)