Answer:
15 years , 12 years , 8 years.
Step-by-step explanation:
Given:
John is 3 years older than Jim.
Jim is 4 years less than twice David’s age.
Ages of three boys add up to 35.
Question asked:
How old are the three boys?
Solution:
Let age of David = 
Let age of Jim = 
Then age of John will be = 
As Jim is 4 years less than twice David’s age
Equation will be ,
Multiplying both side by 2
=
(let equation 1 )
As ages of three boys add up to 35.
Equation will be,
= 
Subtracting both side by 3
=
=
(let equation 2 )
subtracting equation 1 and 2,we get
= 
=
= 
= 
dividing both side by 5
(David ages)
Then ( age of Jim) 

= 
= 
Then age of John will be, 

= 
Thus, age of John = 15 years
Age of Jim = 12 years
Age of David = 8 years