SOLUTION: Ishaan is 2 times as old as Christopher. 35 years ago, Ishaan was 7 times as old as Christopher. How old is Ishaan now?

The equations are

I = 2C,              (1)
I - 35 = 7*(C-35).   (2)

Substitute (1) into (2), replacing/excluding I. You will get

2C - 35 = 7C - 245,

245 - 35 = 7C - 2C  --->  5C = 210  --->  C =  = 42.


Thus we found that Christopher is 42 years old now.


Then Ishaan is 2*42 = 84 years old now.