Question 1143571
Let L = Lester's present age
    J = John's present age

Given: 
1. Lester is older than John by 7 years: L = J + 7
2. 15 years back John's age was 3/4 of Lester's (present) age: J - 15 = 3/4 L

Solution:
I.  L = J + 7
    J - 15 = 3/4L

    L = J + 7
    J = 3/4L + 15

II. L = 3/4L + 15 + 7
    L = 3/4L + 22
    L - 3/4L = 22
 4/4L - 3/4L = 22
        1/4L = 22
    4*(1/4)L = 22*4
           L = 88

Testing the given:  
1. L = J + 7
  88 = J + 7 
  88 - 7 = J 
   J = 81

2. J - 15 = 3/4L
  81 - 15 = 3/4(88)
       66 = 66 

Fifteen years back, John's age (was 66) was 3/4 off Lester's (present) age of 88.



Answer:
Lester's present age is 88 while John's present age is 81.