Answer:
Sally is 63
Step-by-step explanation:
Represent Sally's age by x and Sam's by y.
Then x = 3y and x + y = 84.
Substituting 3y for x in the second equation, we get:
3y + y = 84, or 4y = 84, or y = 21. Since Sally is 3 times as old as Sam, we multiply 21 by 3: Sally's age is 3(21 years) = 63 years
