Assignments
Let
Jill = J
Beth = B
Meg = M
Sounds like Beth is the youngest.
J = M - 2
B = 1/2 M
Explanation
B = 1/2 M. This means that Beth is 1/2 as old as Meg.
J = M - 2 This means that Jill is 2 years younger than Meg.
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Comment
I don't think you can go to three statements. You need one more statement than you've given us.