1) 1-0,4 =0,6
2)7,2:6=1,2 0,72:0,6=7,2:6
ответ:1,2
1) 20/31×2=40/62
20/31×4=80/124
20/31×9=180/279
20/31×10=200/310
2)25/44×3=75/132
25/44×5=125/220
25/44×9=225/396
25/44×11=275/484
(6/5+x)-2/3=13/18
6/5 +x-2/3=13/18
x=13/18-6/5+2/3
x=65/90-108/90+60/90
x=65-108+60/90
x= 17/90