a bag full of gum drops. 2/3 of which are blue. the red drops are 3/8 of the number of blue. There are 3 green drops.

How many drops in the bag?

Are we to assume that there are only 3 colours??

then
blue + red + green = total

let the total be x
(2/3)x + (3/8)(2/3)x + 3 = x
2x/3 + 1x/4 + 3 = x
multiply each term by 12
8x + 3x + 36 = 12x
36 = x

there are 36 drops

check: blue = (2/3)(36) = 24
red : (3/8)(24) = 9
green: 3

24+9+3 = 36