Tom is 2 years older than Sue and Bill is twice as old as Tom. If you add all their ages and subtra

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Tom is 2 years older than Sue and Bill is twice as old as Tom. If you add all their ages and subtract 2, the sum is 20. How old is Bill?

Let t be Tom's age., s be Sue's age, and b be Bill's age. We have the following equations:

1. t = s + 2
2. b = 2t
3. s + t + b - 2 = 20

Get (2) in terms of s
(2) b = 2(s + 2) <-- using (1), substitute for t

So we have (3) rewritten with substitution as:
s + (s + 2) + 2(s + 2) - 2 = 20
s + (s + 2) + 2s + 4 - 2 = 20

Group like terms:
(s + s + 2s) + (2 + 4 - 2) = 20
4s + 4 = 20

Run this through our equation calculator to get s = 4

Above, we had b = 2(s + 2)
Substituting s = 4, we get:
2(4 + 2) = 2(6) = 12
Bill is 12 years old