1)
(1-7/10)х=2
(10/10-7/10)х=2
3/10х=2
х=2:3/10
х=2*10/3
х=20/3
(1-7/10)*20/3=3/10*20/3=2
2)
(1/4+1/5)х=1 4/5
(5/20+4/20)х=1 4/5
9/20*х=9/5
х=9/5:9/20=9/5*20/9
х=4
9/20*4=9/5=1 4/5
3)
(3 1/8+1 3/4)х=2 1/6
(3 1/8+1 6/8)х=2 1/6
4 7/8 * х=2 1/6
39/8*х=13/6
х=13/6:39/8=13/6*8/39
х=4/9
39/8*4/9=39/18=2 3/18=2 1/6
4)
(2 1/12-1 5/6)х=3/4
(2 1/12-1 10/12)х=3/4
3/12*х=3/4
х=3/4:3/12=3/4*12/3
х=3
3/12*3=3/4