The correct answer to this question is A, -5. This answer is found by using the order of operations of math. The acronym PEMDAS is used to represent the order. P stands for parentheses, E for exponents, M for multiplication, D for division, A for addition, and S for subtraction.
In school, the saying Please Excuse My Dear Aunt Sally is used to remember the order. Following the order of operations, the parenthetical values of this question are solved first. Once the costs in between the parentheses are addressed, the rest of the equation can be completed, which gives us the answer -5.
This answer makes no sense. You are saying to do the operation, (2 $ 1), first, then list it as 21. I'm not sure what the $ symbol stands for, but I've never seen a math problem phrased so that you take a subset of 2 integers, and combine them, without using a function. How does (2 $ 1) become 21?