AFCAT I 23 Jan 2025 Shift 1 Paper

We will be needing the concept of quadratic equation to solve.
Calculation:
Let the present age of sister be x
Present age of brother =x+7
Sister's age 5 years ago =x−5
Brother's age 5 years ago =x+2
⇒(x−5)(x+2)=30
⇒x2−3x−10=30
⇒x2−3x−40=0
⇒(x−8)(x+5)=0
⇒x=8
∴ Present age of brother =8+7=15 years