In the 1st one you need to calculate the body's density.
When you do, you'll see it will sink in the 2nd liquid.
Then you just apply Archimedes buoyancy law/thing to calculate the force applied in the body.
The 2nd, you see there are 1449 men with abnormal PSA levels (its more than the 'normal' but ok). of those only a third is expected to have cancer.
the text also says 20% of cancer people dont have abnormal values, so 483 is just 80%. so the final result is