We need to use order of precedence of operators to evaluate it.
BoDMAS acronym to remember order of precedence of operators
Bracket of Division Multiplication Addition Subtraction
Since multiplication has greater precedence, we evaluate it first
33+ 1 · 9 +12 = 33+9+12
now, all the operators are in same level of precedence. so, adding them together we have
33+9+12 = 54
∴ 33+ 1 · 9 +12 = 54