1.
14/17 * 34/21=(7*2*2*17) / (17*7*3)=4/3=1 1/3
12/25 * 5/19 * 57/36=(12*5*3*19) / (5*5*19*12*3)=1/5
3 4/7 * 8 2/5=25/7 * 42/5=(5*5*7*6) / (7*5)=5*6=30
8/11 * 12 5/6=8/11 * 77/6=(2*4*11*7) / (11*2*3) = 28/3=9 1/3
7/15 * 35=(7*5*7) / (5*3)=49/3=16 1/3
2.
7/18 a +1/12 a +5/18 a=12/18 a+1/12 a=24/36 a+3/36 a=27/36 a=(9*3)/(9*4) a=3/4 a
при а=1 5/7
3/4 * 1 5/7=3/4 * 12/7=9/7=1 2/7