plural of sum
"The teacher graded all the math sums on the board before dismissing the class."
Third-person singular simple present indicative form of sum
"She sums the numbers on her calculator before checking the receipt."
In plain English: To sum something up means to add numbers together to get their total.
"She sums up her grocery bill quickly on the calculator before paying at the counter."
plural of Sum
"The teacher asked us to check our sums before turning in the worksheet."