The answer is the last option =SUM(A1+B1)
There should be an equals sign (=) before any formula in excel. In solving for math function, you should also enclose the values within the parentheses ( ... ). If you're adding two numbers, you can use =SUM(A1+B1). If you're adding multiple numbers, use the colon sign (:) ex. =SUM(A1:D1)
