It's more likely that this should've read: ".........15 years back John's age was 3/4 of Lester's age," then/at that time!
Having said that, that person's answers are INCORRECT.
Correct answers:
Let L be the Lester's age; then the John's age is L-7 years. 15 years back John's age was ((L-7)-15) = L-21; Lester's age was L-15 years. The condition says L - 22 =. Solve this equation step by step. Start multiplying both sides by 4. 4L - 88 = 3*(L-15) 4L - 88 = 3L - 45 4l - 3L = 88 - 45 L = 43. ANSWER. Lester is 43 years old; John is 43 - 7 = 36 years old. CHECK. 43 - 15 = 28; 36 - 15 = 21; 21 = . ! Correct !