Question

Mary is 21 years old. Her age is 9 years more than 3 times Henry's age. Which equation can be used to determine x, Henry's age in years?

9 +21= 3x

x + 9 = 21

21+x=3(9)

3x + 9 = 21

Answer 1

3x + 9 = 21

Explanation:

Let Henry's age be x

Mary's age = 9 + 3x

21 = 9 + 3x

Can also be written as 3x + 9 = 21