Every marble in a jar has either a dot, a stripe or both. The ratio of striped marbles to non-striped marbles is 3:1, and the ratio of dotted marbles to non-dotted marbles is 2:3. If six marbles have both a dot and a stripe, how many marbles are there all together?

Answer 1

If there are
x with stripe only
y with dot only
z with stripe and dot,

z = 6
(x+z) = 3y
3(y+z) = 2x

So,
x+y+z = 40