First establish variables for current age.
Clive's current age = c
Sherman's current age = s
"Three years ago,"
Clive was: (c - 3)
Sherman was: (s - 3)
"Sherman was twice as old as Clive."
(s - 3) = 2(c - 3)
Then in terms of Sherman's present age, distribute 2, combine like terms
s - 3 = 2c - 6
s = 2c - 6 + 3
s = 2c - 3
