Solvego - Math Game comes from Halil Salis. The objective: how fast can you find the order of operations to get the target number.
The easy mode: 3 numbers are given.
The medium mode: 4 numbers are given.
The hard modes: 5 numbers are given.
Like a lot of puzzle apps out there, nobody is playing this game. I think there are less than 60 people on the Leaderboard.
A more polished version of this is Qwhizzle which isn't quite the same, but very similar.
Other Good Math Puzzles
Divide By Sheep
Qwhizzle - love this game.
Cracking the Safe