I= Ishaan's age= 2C
C= Christopher's age
35 years ago means we have to subtract 35 from their current age. Ishaan minus 35 equals 7 times Christopher minus 35 years.
CHRISTOPHER'S AGE:
I - 35= 7(C-35)
substitute I=2C in for I
multiply 7 by all in parenthesis
2C - 35= 7C - 245
add 35 to both sides
2C= 7C - 210
subtract 7C from both sides
-5C = -210
divide both sides by -5
C= 42 Christopher's age
ISHAAN'S AGE:
I= 2C
substitute C=42 to find Ishaan's age
I= 2(42)
I= 84 Ishaan's age
CHECK:
Substitute answers in original equation
I - 35= 7(C-35)
84 - 35= 7(42-35)
49= (7*42)+(7*-35)
49= 294-245
49=49
Hope this helps! :)