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1) х=3/20:(1ц4/5)=3/20:9/5=3/20*5/9=1/4*1/3=1\12

2)4/5*х=1ц2/5-1ц1/3

4/5*х=7/5-4/3

4/5*х=21/15-20/15

4/5*х=1\15

х=1/15:4/5=1/5*5/4=1/4

3)х+3/4=3ц2/3:4ц2/5

х+3/4=11/3: 22/5

х+3/4=11/3*5/22

х+3/4=5/6

х=5/6-3/4=10/12-9/12=1/12