A) (4/5 - 11/15) 5/11
= (12/15 - 11/15) 5/11
= 1/15 * 5/11
= 5/165
= 1/33

B) 7/88 (8/21 + 8/7)
= 7/88 (8/21 + 96/21)
= 7/88 * 104/21
= 728/1848
= 91/231