Solution:

8

Solution:

86,888

Solution:

14

Solution:

1 2 and 3

Explanation:
1 + 2 + 3 = 1 * 2 * 3 = 6

Solution:

1 or -1

Solution:

15

Solution:

.05

Given the equation 8/x = 160, when you solve for x, you indeed get:

8/x = 160

To find x, you can simply invert the fraction:
x/8 = 1/160

Now, to isolate x, multiply both sides by 8:
x = 8 * (1/160)
x = 8/160
x = 1/20 = 0.05

Solution:

2519

The number has to end in 9.
Looked brute force for small numbers.
59 and 119 were promising, but no cigar.

Then looked for agreement among
39 + multiples of 40,
69 + multiples of 70 and
89 + multiples of 90
Smallest one was 2519.

Solution:

143547

Solution:

9376

Looking at the last digit, the last digit must be either 0, 1, 5 or 6.
Then looking at the last two digits, the last two digits must be either 00, 01, 25 or 76.
Then looking at the last three digits, the last three digits must be either 000, 001, 625 or 376.
Then looking at the last four digits, the last four digits must be either 0000, 0001, 0625 or 9376.
Out of those, only 9376 is a 4 digit number