the distributive property is when the coefficient in front of the parentheses is applied to both terms inside.
a. distribute the 6 to make 6xa+6x5. simplify to make 6a+30
b. distribute the 12 to make 12x4+12x3a. simplify to make 48+36a
c. distribute the c to make (1/2)xb-(1/2)x12. simplify to make (b/2)-6