Question

The sum of Pete's and Sam's ages is 30. Five years ago, Pete was 3 times as old as Sam. How old is Sam?



Let P = Pete's age, S = Sam's age, and P + S = 30. Which of the following equations would complete the system?

P - 5 = 3S
P - 5 = 3S - 5
P - 5 = 3S - 15

Answer 1

P + S = 30
since five years ago, Pete was /three times/ as old as Sam...
P-5=3S-5
you have to subtract 5 from both sides, or else the equation would not be equal.