a = 18
b + c = 57
a) a + b + c =
18 + 57 = 75
b) a + 5 × b + 5 × c =
18 + 5 × ( b + c ) =
18 + 5 × 57 =
18 + 285 = 303
c) 3 × a + 2 × b + 2 × c =
3 × 18 + 2 × ( b + c ) =
54 + 2 × 57 =
54 + 114 = 168
d) a × b + a × c + 7 × b + 7 × c =
a × ( b + c ) + 7 × ( b + c ) =
18 × 57 + 7 × 57 =
57 × ( 18 + 7 ) =
57 × 25 = 1425