Question

Jim, Carla and Tommy are members of the same family. Carla is 5 years older than Jim. Tommy is 6 years older than Carla. The sum of their three ages is 31 years. How old is each one them?

Answer 1

So,

We'll solve it with only one placeholder, since that's simpler.

Jim's age = J
Carla's age = C
Tommy's age = T

J = base
Carla's age = J + 5
Tommy's age = Carla's age + 6 or J + 5 + 6 or J + 11

Sum of ages = 31
(J) + (J + 5) + (J + 11) = 31

3J + 16 = 31

Subtract 16 from both sides
3J = 15

Divide both sides by 3
J = 5

Carla's age = J + 5
Carla's age = 10

Tommy's age = Carla's age + 6
Tommy's age = 10 + 6 or 16

5 + 10 + 16 = 31
15 + 16 = 31
31 = 31 This checks.

Jim is 5.
Carla is 10.
Tommy is 16.

Answer 2

Lets
Jim  x years old
Carla (x+5) years old
Tommy (x+5)+6 years old
sum is x+(x+5)+(x+5)+6=31 years old
3x+16=31
3x=15
x=5 - age of Jim
x+5=5+5=10 - age of Carla
x+5+6=16  - age of Tommy
Answer: 5, 10 and 16 y.o