12 + 19 + 18 + 32 + 19
= 12 + 18 + 19 + 32 + 19
= 30 + 19 + 32 + 19
= 49 + 32 + 19
= 81 + 19
= 100
12 + 19 + 18 + 32 + 19
= ( 12 + 19 ) + ( 18 + 32 ) + 19
= 31 + 50 + 19
= 81 + 19
= 100
Cách 2 : 12 + 19 + 18 + 32 + 19
= 12 + ( 19 + 19 ) + ( 18 + 32 )
= 12 + 38 + 50
= 50 + 50
= 100
12 + 19 + 18 + 32 + 19
= 19 + [ 12 + 18 + 32]
= 19 + 62
= 81
=(12+18)+(19+32+19)
= 30 + (38+32)
= 30 + 70
= 100