Question 57582
we can write a simple linear equation to solve

let x be the age of the son.

since the father is 3x the sons age 10 years ago x+3x=80 the sum of ages is 80 because the father and son increased by 10 years to make the sum 100.

so 4x=80

divide by 4 to isolate x

x=20

the son 10 years ago was 20, the father was 60. so at present day, add 10 to each of them,

at present day the son is 30 and the father is 70.