Cách 1: 29 . (19 – 13) – 19 . (29 – 13) = 29 . 6 – 19 . 16 = 174 – 304 = –130.
Cách 2: 29 . (19 – 13) – 19 . (29 – 13)
= 29 . 19 – 29 . 13 – (19 . 29 – 19 . 13)
= 29 . 19 – 29 . 13 – 19 . 29 + 19 . 13
=(29 . 19 - 19 . 29) + (19 . 13 - 29 . 13)
= 13 . (19 – 29) = 13 . (–10) = –130.