Answer:
6 years old
Step-by-step explanation:
First, turn the information given in words as equations. Use variables to represent the people:
let A be Addison's age
let B be Bailey's age
let C be Christopher's age
A = 3B (Addison is 3 times as old as Bailey)
B = 2.5C (Bailey is 2.5 times as old as Christopher)
A + B + C = 66 (the sum of their ages is 66) (sum means addition)
Start with the equation for the sum of their ages (A + B + C = 66). You have other equations that can replace the variables in this equation.
A + B + C = 66
(3B) + B + C = 66 Replace A with 3B (because A = 3B)
4B + C = 66 Collect like terms (3B + B = 4B)
4(2.5C) + C = 66 Replace B with 2.5C (because B = 2.5C)
10C + C = 66 Collect like terms (10C + C = 11C)
11C = 66 Isolate "C"
11C/11 = 66/11 Divide both sides by 11 to cancel out 11 on the left side.
C = 6 Christopher's Age
Therefore Christopher is 6 years old.
