1) х-2 1/5=5 1/20
х-(2*5+1)/5=(5*20+1)/20
х-11/5=101/20
х=101/20+11/5
х=101/20+(11*4)/(5*4)
х=101/20+44/20
х=145/20 сократим на 5
х=29/4=7 1/4
2) 10 2/7-х=2 1/2
х=10 2/7-2 1/2
х=(10*7+2)/7-(2*2+1)/2
х=72/7-5/2
х=(72*2)/(7*2)-(5*7)/(2*7)
х=(144/14)-(35/14)
х=(144-35)/14
х=109/14=7 11/14
3) х+4 2/3=6 1/4
х=6 1/4-4 2/3
х=(6*4+1)/4-(4*3+2)/3
х=(25/4)-(14/3)
х=(25*3)/(4*3)-(14*4)/(3*4)
х=(75/12)-(56/12)
х=(75-56)/12
х=19/12=1 7/12