To find the values of x in each proportion, we can cross multiply and solve for x.

1) 2x + 1 : 8 = 2 : 1
Cross multiplying:
(2x + 1) 1 = 8 2
2x + 1 = 16
2x = 15
x = 7.5

2) 3x - 1 : 3 = 2 : 8
Cross multiplying:
(3x - 1) 8 = 3 2
24x - 8 = 6
24x = 14
x = 14/24 or x = 7/12

3) 1 : 4 = 2x - 1 : 2
Cross multiplying:
1 2 = 4 (2x - 1)
2 = 8x - 4
8x = 6
x = 6/8 or x = 3/4

I hope this helps! Let me know if you need further assistance.