Ten years ago Linda was three times christys age then. Ten years from now christys age will be 4/7 of Linda’s age then. How old are they now.
This is as clear as "daylight," so I don't know how 1 of these people didn't get it. It's not
surprising though, considering the vast number of wrong answers he/she has been known to produce.
Let Christy's and Linda's ages, be C and L, respectively
Then 10 years ago, Christy was C - 10, while Linda was L - 10
We then get their AGE equation, 10 years ago as L - 10 = 3(C - 10)____L - 10 = 3C - 30___L = 3C - 20 ----- eq (i)
In 10 years' time, Christy will be C + 10, while Linda will be L + 10
We then get their AGE equation, 10 years from now, as
7C + 70 = 4(L + 10) ------ Multiplying by LCD, 7
7C + 70 = 4L + 40
7C - 4L = - 30 ------ eq (ii)
7C - 4(3C - 20) = - 30 ----- Substituting 3C - 20 for L in eq (ii)
7C - 12C + 80 = - 30
- 5C = - 110'
Christy's age, or
Knowing Christy's age, you can now find Linda's age using eq (i)!