Afather who is 42 years old has a son and a daughter. the daughter is three times as old as the son. in 10 years the sum of all their ages will be 100 years. how old are the two siblings at present?

The ages at present are:

Explanation:

Translate the word language to algebraic expressions.

1) A father who is 42 years old has a son and a daughter.

2) The daughter is three times as old as the son.

3) In 10 years the sum of all their ages will be 100 years

            ↑                          ↑                                  ↑                             ↑

age of the father     age of the son          age of the daughter      sum

4) How old are the two siblings at present:

Solve the equation

        4x = 100 - 72

        4x = 28

        x = 28 / 4

        x = 7

5) Answers:

6) Verification:

        age of the son: 7 + 10 = 17

        age of the daughter: 21 + 10 = 31

        age of the father: 42 + 10 = 52

        sum of the ages: 17 + 31 + 52 = 100 ⇒ correct.

step-by-step explanation: