1) 5/6*7/9=5*7/6*9=35/54
11/28*7/33=11*7/28*33=77/924=7/84
1 8/25*1 4/13=33/25*17/13=33*17/25*13=561/325=1 236/325
3 5/7*1 1/13=26/7*14/13=26*14/7*13=364/91=4
2)1 5/19*(6-3 5/8)=24/19*(3-5/8)=24/19*2 3/8=24/19*19/8=3
1,8*(6,3*1,4-2,05)=1,8*(8,82-2,05)=1,8*6,77=12,186