1)(3/4+1/20)*1/2=(15/20*1/20)*1/2=16/20*1/2=8/20=4/10=2/5
2)(7/12-1/3)*16/19=(7/12-7/12)*16/19=0*16/19=0
3) 5 5/15*9/32=5 1/3*9/32=16/3*9/32=3/2=1 1/2
4)(11/24+1/6)*1 3/5=(11/24+4/24)*1 3/5=15/24*8/5=3/3=1
5)(5 1/2+3/5)*5/9=(5 5/10 +6/10)*5/9=(55/10+6/10) *5/9=61/10*5/9=61/18=3 7/18
6)(7-2 5/16)*4/25=(6 16/16-2 5/16)*4/25=4 11/16*4/25=75/16*4/25=3/4