Question

Ca(OH)2 + H3PO4 = Ca3(PO4)2 + H2O

Answer 1

Make a quick chart with each element represented, and count them up. HINT - leave the polyatomic anions together - in this case, PO4

Left      Right
1     Ca  3
2      O   1
5      H   2
1    PO4 2

Begin by balancing like finding common denominators of fractions - apply to both sides:
I started by adding a 2 in front of H3PO4 on the left, them 6 in front of H2O on the right. Last, a 3 in front of Ca (OH)2. Then, re-count using the chart format to make sure you're right.

3Ca(OH)2 + 2H3PO4 = Ca3(PO4)2 + 6H2O