For this item, we let x be Maya's age. By the representation, Adrian age will be,
0.5x +4
And that Lin's age will become,
0.5x + 4 - 7
Summing up all the ages,
x + (0.5x + 4) + (0.5x - 3) = 61
The value of x from the equation is 30. Therefore, Lin's age is,
0.5(30) - 3 = 12