7,2-4 8/9; 0,21*3 2/7; (1.4-1/6)*2 1/7

=7 1/5-4 8/9=7 9/45-4 40/45=6 54/45-4 40/45=2 14/45 =21/100*23/7=69/100=0,69 =(1 2/5-1/6)*2 1/7=(1 12/30-5/30)*2 1/7=1 7/30*2 1/7=37/30*15/7=37/14= =2 9/14