a,A=(1/3 - 8/15 - 1/7 ) + [ 2/3 + ( -7/15) + 1 1/7]

= 1/3 -8/15 - 1/7 + 2/3 - 7/15 + 8/7

= (1/3 + 2/3) - (8/15 + 7/15) - (1/7 - 8/7 )

= 1 - 1 + 1

= 1

b,B= 0,25 + 3/5 -( 1/8 -2/5 + 1 1/4 )

= 1/4 + 3/5 - ( 1/8 - 2/5 + 5/4)

= 1/4 + 3/5 - 1/8 + 2/5 - 5/4

= (1/4 - 5/4 ) + ( 3/5 + 2/5 ) - 1/8

= -1 + 1 - 1/8

= 0 - 1/8

= -1/8

4/1.4 + 4/4.7 + 4/7.10 +...+ 4/94.97 + 4/97.100 =4/3 . ( 3/1.4 + 3/4.7 + 3/7.10 +...+3/94.97 + 4/97.100) =4/3 . ( 1 - 1/4 + 1/4 - 1/7 + 1/7 - 1/10 +...+1/94 - 1/97 + 1/97 - 1/100) =4/3 . ( 1- 1/100 ) =4/3 . 99/100 =33/25