Not sure how to solve:

If a sugar solution has a density of 0.98 g/cm^3, what is the percent mass sugar content?
Thanks
-MC

The only way this can be done that I know of is to have at hand a calibration curve for sugar solutions. If you have such a curve (% sugar on one axis and density on the other) you can read % sugar from the graph.

I'm a little surprised that the density is < 1.00g/cc although you didn't list the temperature. That may (or may not be) why.