Answer:
Jeri is 13, and thus Theresa is 9 and Laura is 16.
Step-by-step explanation:
Let's start by declaring variables
D - dad's age
L - laura's age
J - jeri's age
T - theresa's age
The first statement tells us that D = L + J + T
Jeri being 4 years older than Theresa gives us
J = T + 4
Jeri being 3 years younger than Laura gives us
J = L - 3
So notice that the common variable in these two equations is J. So if we can represent every girls age in terms of Jeri's, we will be down to one variable. So
T = J - 4
L = J + 3
Now, we can rewrite the original equation using only J's
38 = (J + 3) + J + (J - 4)
38 = 3J - 1
39 = 3J
13 = J
So Jeri is 13, and thus Theresa is 9 and Laura is 16.
