a) 2 x (5 + 6) = 2 x 9 + 2 x 7 = 18 + 14 = 32
b) 2 x ( 3 + 4) + 2 x ( 4 + 5) + 2 x ( 5 + 6) =
= 2 x 7 + 2 x 9 + 2 x 11 =
= 14 + 18 + 22 =
= 32 + 22 =
= 54
