a solder consists of 67% lead and 33% tin. What is the mass of lead in
a 250 gram block of solder, and why?

It seems quite simple, if the percentage of lead in solder is measured
in mass, then the mass of lead is 250 gram x 67% = 167 gram

I make it one hundred and sixty seven and a HALF grams

But if the 67/33 ratio is based on weight, the mass of lead  - being
heavier - will be less.  You have to find the specific gravity of lead
and tin and calculated what mass/volume of lead equals 167.5 grams.

By the way, it might not be a chemistry problem, but a physics
problem, :). To calculate more accurately, my answer should be 167.5
gram.

Umm, myoarin I think you wanted to say volume not weight. Assuming you do 
all your weight measurements on the same place then gravity is constant and
mass ratio=weight ratio (since weight=mass*gravity).

However this is very unlikely for solids (only liquids may be mixed using volume) 
so the answer pegasusplus and kemlo gave (167.5 g) is correct.

And yes, this is a physics problem. No chemical reaction happens here.