1) 7,2 * (х-2,8)=1
7,2x-20,16=1
7,2x=1+20,16
7,2x=21,16
x=21,16/7,2
x=2116/100:72/10
x=19044/125
2) 4/5 * (12 1/3-х)=1
4/5*37/3-4/5x=1
148/15 - 4/5x=1
-4/5x=1-148/15
-4/5x=-133/15
4/5x=133/15
x=133/15:4/5
x=133/15*5/4
x=133/12
x=11 1/12
3) 0,7 * (х+2/5)=1
7/10x+7/25=1
7/10x=1-7/25
7/10x=18/25
x=18/25:7/10
x=63/125
4) (х-1 2/3) * 1/4=1
1/4x-5/4*1/4=1
1/4x-5/8=1
1/4x=1+5/8
1/4x=13/8
x=13/2
x=6 1/2
5) 1,3 * (15 3/4 - х)=1
13/10*63/4-13/10x=1
819/40-13/10x=1
-13/10x=1-819/40
-13/10x=-779/40
13/10x=779/40
x=779/40:13/10
x=779/52
x=14 24/52
6) (х+2 5/7) * 1/5=1
1/5x+ 19/7*1/5=1
1/5x+19/35=1
1/5x=1-19/35
1/5x=16/35
x=16/35:1/5
x=16/7
x=2 2/7