how old is Jeri?

Question

Dad's age is equal to the sum of Laura's, Jeri's and Theresa's ages. If Jeri is 4 years older than Theresa and 3 years younger than Laura, and Dad's age is 38 years, how old is Jeri?

Answer 1

Let's set up the equations we'll need to solve this

equation 1 for Dad's age is equal to the sum of Laura's, Jeri's and Theresa's ages: D = L + J + T

equation 2 for Jeri is 4 years older than Theresa: J = T + 4

equation 3 for Jeri is 3 years younger than Laura: J = L - 3

Since Dad's age is 38 years, L + J + T = 38.

Let's put equations 2 and 3 in terms of J to get T = J - 4 and L = J + 3 respectively.

Now substitution for L and T into equation 1 gives (J + 3) + J + (J - 4) = 38. Now solve for J: 3J - 1 = 38 so 3J = 39 and J = 13.

Answer 2

jeri is 13