Order of Operations is about the priority of Parentheses, Exponents, Multiplication, Division, Addition and Subtraction when they they appear together in a Maths expression. The acronym PEMDAS is a reminder of the order of priority. The Expressions A and B don't need parentheses because multiplication has priority over addition, you multiply 3 x 5 before adding the 4. Many people are tricked into adding first and give 35 as the answer to A and 56 as the answer to B. A = 19 and B = 20.
When it is necessary to force addition or subtraction before the multiplication, parentheses are used. People are less likely to get C, D and E wrong because of the parentheses. C = 35, D = 27 and E = 14.
