Hi Charon.

Ratios are fractions, and so are percentages.

For example,

And when you have a fraction of a percentage, then you have a fraction of a fraction, so you can think of it as multiplying by the inverse of the reciprocal of the denominator, like this:

I presume by the double colon, you mean equals. So the question is really asking this:

Try simplifying the fractions first, then isolate x, then "invert and multiply" to find the answer.

Cheers,
Stephen La Rocque.