Dear student
Let Renu 's age be x years and Renu 's mother 's age be 4x years.
After five years, Renu 's age=x+5 years Renu 's mother 's age=4x+5 yeras
According to the question,
3(x+5)=4x+5
3x+15=4x+5
4x-3x=15-5
x=10
Renu 's age= 10 years
Renu 's Mother 's age= 4*10 = 40 years