Question

a and b are together 90 year old . Five year ago ,A was thrice as old as B was hence the age of A and B five year ago would be x-5 years and (85-x)years respectivly

Answer 1

let present age of a =x
present age of b=y
five years ago ...
x-5=3y-5
x+y=90
y=90-x
so ...
x-5= 3(90-x)-5= 180-3x-5= 175-3x
4x= 180
x= 90/2=45
y= 45

Answer 2

Answer:

Let us assume age of A be y years. So, age of B = (90 – y) years. Then, Before 5 years A’s age = (x – 5) years and B’s age = (90 – x – 5) = (85 – x) years.Read more on Sarthaks.com - https://www.sarthaks.com/849112/a-and-b-are-together-90-years-old-five-years-ago-a-was-thrice-as-old-as-b-was