7/11 + 3/4 + 4/11 +1/4
= ( 7/11 + 4/11 ) + ( 3/4 + 1/4 )
= 1 + 1
= 2
72/99 - 28/99 - 14/99
= 72/99 - ( 28/99 + 14/99 )
= 72/99 - 42/99
= 50/99
69,78 + 35,97 + 30,22
= ( 69,78 + 30,22 ) + 35,97
= 100 + 35,97
= 135,97
83,45 - 30,98 - 42,47
= 83,45 - ( 30,98 + 42,47 )
= 83,45 - 73,45
= 10