При каком значении b уравнение bx+6=5x+4(1-x) не имеет корня?

1)
х га - в первый день
7/9 х га - во второй

х+7/9 х=240
1 7/9 х =240
х= 240:1 7/9=240 * 9/16
х=270/2=135 (га)-вспахали в первый день
240-135=105(га)-во второй

2.
1) 1 4/5 : 3/4=9/5 * 4/3=12/5=2 2/5(т.руб./кг)-стоимость конфет
2) 2 1/2 * 2 2/5=5/2 * 12/5=6(т.руб.)-заплатят за 2 1/2 кг

3.
1/6 х+5/12 х=8 4/10
2/12 х+5/12 х=8 2/5
7/12 х= 8 2/5
х= 8 2/5 : 7/12=42/5 * 12/7
х=72/5=14 2/5

4.
5/9+mn=(5+9mn)/9

5.
5 2/3 : 1/3 - 1 7/12 * 2=13 5/6

1) 5 2/3 : 1/3=17/3 * 3/1=17
2) 1 7/12 * 2=19/12 * 2=19/6=3 1/6
3) 17-3 1/6=16 6/6 - 3 1/6=13 5/6

15 * 3 = (10 + 5) * 3 = 10 * 3 + 5 * 3 = 30 + 15 = 45

17 * 3 = (10 + 7) * 3 = 10 * 3 + 7 * 3 = 30 + 21 = 51

4 * 14 = 4 * (4 + 10) = 4 * 4 + 4 * 10 = 16 + 40 = 56

7 * 13 = 7 * (10 + 3) = 7 * 10 + 7 * 3 = 70 + 21 = 91

43 * 5 = (40 + 3) * 5 = 40 * 5 + 3 * 5 = 200 + 15 = 215

33 * 6 = (30 + 3) * 6 = 30 * 6 + 3 * 6 = 180 + 18 = 198

3 * 48 = 3 * (40 + 8) = 3 * 40 + 3 * 8 = 120 + 24 = 144

7 * 27 = 7 * (20 + 7) = 7 * 20 + 7 * 7 = 140 + 49 = 189

28 * 3 = (20 + 8) * 3 = 20 * 3 + 8 * 3 = 60 + 24 = 84

39 * 3 = (30 + 9) * 3 = 30 * 3 + 9 * 3 = 90 + 27 = 117

6 * 86 = 6 * (80 + 6) = 6 * 80 + 6 * 6 = 480 + 36 = 516

9 * 37 = 9 * (30 + 7) = 9 * 30 + 9 * 7 = 270 + 63 = 333

120 * 4 = (100 + 20) * 4 = 100 * 4 + 20 * 4 = 400 + 80 = 480

140 * 5 = (100 + 40) * 5 = 100 * 5 + 40 * 5 = 500 + 200 = 700

320 * 4 = (300 + 20) * 4 = 300 * 4 + 20 * 4 = 1200 + 80 = 1280

460 * 2 = (400 + 60) * 2 = 400 * 2 + 60 * 2 = 800 + 120 = 920