The marbles are divided into 4 + 5 = <<4+5=9>>9 parts.
Each part consists 36/9 = <<36/9=4>>4 marbles.
So Manny had 5 parts x 4 = <<5*4=20>>20 marbles.
After giving 2 marbles to his brother, he now has 20 - 2 = <<20-2=18>>18 marbles left.
#### 18