Math
posted by Craig .
Matt has twice as many stickers as David. If David has d stickers, and Matt gives David 10 stickers, how many stickers does each have in terms of d?

m = 2 d (initially)
After Matt gives Dave 10, they have new amounts m' and d'.
m' = 2 d  10
d' = d + 10 
David: d stickers
Matt: 2d stickers
after giveaway ...
David : d+10
Matt : 2d  10
The question is not clearly stated.
Since you used the present tense throughout, one is forced to wonder if Matt "has" twice a many as David before or after the transfer.
I actually interpreted it as
Matt had twice .....