Answer:
Hello,
Step-by-step explanation:
I am just reply to see if i really understand that problem
Let's assume s the present age of the son, and f the present age of the father.
[tex]\begin {array}{c|c|c}&son&father\\now&s&f=3*s\\in\ 10\ years&s+10&f+10\\\end{array}[/tex]
The age of the son After 10 years is equal to the age of the father before 20 years:
s+10=f+10-20
f=3s
=> s+10=f-10
=> s+10=3s-10
=> 2s=20
=> s=10 and f=30
