Если правельно написано то все они подобные слогаемые
1 1/2-2/3=3/2-2/3=(3*3-2*2)/6=5/6.
<span>х+(90+30)=180
x + 120 = 180
x = 180 - 120
x = 60
60 + (90 + 30) = 180
180 = 180
(x + 90) + 30 = 180
x = 180 - 90 - 30
x = 60
(60 + 90) + 30 = 180
180 = 180
(x + 60) *5 = 500
5x + 300 = 500
5x = 500 - 300
5x = 200
x = 200 : 5
x = 40
(40 + 60) * 5 = 500
500 = 500
5*x + 300 = 500
5x + 300 = 500
5x = 500 - 300
5x = 200
x = 200 :5
x = 40
5 * 40 + 300 = 500
500=500</span>
А) 2.6+7х=68
7х=68+2.6
просто. оеши