Question

Which equation best represents this situation?

The sum of 21 and an unknown number is equal to 30.

A. 21b = 30

B. 21 + b = 30

C. 21 ÷ b = 30

D. 21 - b = 30

Answer 1

The answer is B. 21 + b = 30

Answer 2

Well, the sum of two numbers can be found by adding them together. SO, the answer would be the second choice, B. 21+b=30.
The product of two numbers means multiplication, the difference between two numbers means subtraction, and the quotient of two numbers is found by dividing them.