1) 11+ 2*х=21
2) х-16=8*х
3) 100-х*8=6*х
4) -21-1,7*х=41,4+3,5*х

1) 11 + 2x = 21

2x = 21 - 11

2x = 10

x = 5

2) x - 16 = 8x

8x - x = -16

7x = -16

x = -16/7 = -2 2/7

3) 100 - 8x = 6x

6x + 8x = 100

14x = 100

x = 100/14 = 7 2/14 = 7 1/7

4) -21 - 1,7x = 41,4 + 3,5x

3,5x + 1,7x = -21 - 41,4

5,2x = -62,4

x = -12