Answer:
The linear equation satisfying the given condition is,

where x is Ravi's age and t is the number of years
(after 10 years (t=10) his age becomes 25)
Explanation:
Let x be Ravi's age
Now, his current age is unknown, but if you add 10 to it, then it becomes 25, so
x + 10 =25
so, his current age is x = 25 =10
x = 15
Now, we find the linear equation satisfying the given condition,
Let t be the number of years that have passed since the present time
so, if 0 years have passed, his age will be 15 years
after 1 year, his age will be 16 years
after 10 years, his age will be 25 years and so on
so

this satisfies the given condition, since if we add ten years i.e t = 10,
then we get 25