решите пожалуйста 3 (а, б)

19/9*3/7+21/4*8+
+(82/15*1/41-5/2*4/15)=
19/21+42+(2/15-2/3)=
=42 19/21-8/15=
=42 95/105-56/105=
=42 39/105=42 13/35

45/7*7/9*10/3/1*4/21*4/21=
=50/3*441/16=25*147/8=
=3675/8=459 3/8