Умножим первое уравнение на -3:
- x/4 - 3y/5 = -24
x/4 - y/7 = -2
сложим
-26y/35 = -26
x/4 - y/7 = -2
y = 35
x/4 = -2 + 5
y = 35
x = 12
3/11=0,(27)
3/4=0,75
3/11 <x<3/4
x={0.26.....0.74}
x=0.3, х=0,6
1/6 х+2/9 - 0,25*5/9=1/6 х+2/9 - 1/4 * 5/9=1/6 х+2/9 - 5/36=1/6 х+8/36 - 5/36=1/6 х+3/36=1/6 х+1/12
при х=6
1/6*6+1/12=1+1/12=1 1/12
х+9,14= 5*7,2
х=36-9,14
х=26,86
А) 3/8+5/16 = 6/16 + 5/16 = 11/16
б) 5/18 + 2/9 = 5/18 + 4/18 = 9/18
в) 4/7 + 3/14 = 8/14 + 3/14 = 11/14
г) 7/100 + 3/10 = 7/100 + 30/100 = 37/100