How many moles of calcium are required to produce 60.0 g of calcium phosphate?

for any compound (say HX). Calculate total molar m (of HX). Then if it asks m of X in given sample, THEN, find the weight of X in one mole of HX. Then, it becomes a ratio problem. If in Z gm of HX, there is Y gm X. So in K gm HX, wt of X is (Y/Z) * K gm. hope it helps. :)