Use model drawing method.
Draw a big box to represent the coins Amy has.
Since ken has 4 more coins, draw a big box and a small box with 4 inside.
Next, draw a line outside to show that the coins add up to 36 coins.
Since we know the smalle box has 4 coins, we take it away.
Thus, we will have 2 big boxes, and a total of 32 coins.
2 big boxes is 32 coins, so 1 big box will be 16 coins.
Hence, the answer is 16.