The sum of two numbers is 28. The first number is 7 more than twice the second number. Let a represent the first number. Let b represent the second number. What is the second number? Use the table to guess and check.

7

Step-by-step explanation:

We can represent this with an equation. a+b = 28, and a = 7 + 2b. We can substitute the second equation into the first equation to get 7 + 2b + b = 28, or 7 + 3b = 28. Subtract 7 from both sides and we get 3b = 21. Divide both sides by 3 and we get b = 7. Therefore, the second number is 7.