Question

A father 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?

Please help quick!
D = 3S

(42+10) + S+10 + D+10 = 100

Substitute 3S for D in the second equation and solve for S. Insert that value into the first equation to solve for D. Check by putting both values into the second equation.
(42+10)+(s+10)+(d+10)=100
72+s+d=100
s+d=28

d=3s so you can plug it in
s+3s=28
4s=28

s=7
d=22
d=21* sry

Related Questions

A. A woman was 30 years old when her daughter was born.Her age is now 6 years more than three times... the age of the father is square of the age of his daughter . five years hence the fathers is three t... A father is five times older than his daughter. After 10 years he will be twice as old as his daught... What inference can be made based on the daughter’s actions in this passage? The daughter was look...