Re-arrange the coins from the diamond shape so the coins are 4 in a row (it may be a slanted line). In each move, you have to slide a coin into a new position that is touching 2 other coins.
Add 4 matchsticks to divide the triangle into 3 equal parts. The 3 parts may differ in shape but must be equal in size.
Move 3 matchstick so coin is inside the house (same shape).
Move 2 coins so every coin touches exactly 3 coins.
Move 1 coin to form 2 lines of 4 coins.
