1) -1=7,2-2,4х
2,4х=7,2+1
2,4х=8,2
х=8,2:2,4
х=82/10*10/24
х=82/24
х=41/12
х=3 5/12
2) 2/3=7,2-2,4х
2,4х=7,2-2/3
24/10х=72/10-2/3
24/10х=72*3/30-20/30
24/10х=216-20/30
х=196/30 : 24/10
х=196/3*24
х=196/72
х=49/18
х=2 13/18
3) 5=7,2-2,4х
2,4х=7,2-5
2,4х=2,2
х=22/10:24/10
х=22/24
х=11/12