To solve this expression, we first simplify the fractions:

1/6 + 1/10 + 1/15 = 5/30 + 3/30 + 2/30 = 10/30 = 1/3

Next, we simplify the fractions on the right side of the equation:

3/5 - 1/3 - 1/4 = 12/20 - 20/60 - 15/60 = 36/60 - 20/60 - 15/60 = 1/60

So the final expression is:

1/3 : 1/60

To divide fractions, we multiply by the reciprocal of the second fraction:

1/3 ÷ 1/60 = 1/3 * 60/1 = 60/3 = 20

Therefore, the answer is 20.