Question 153985
16. The difference of three times a number and 16 is at least 8.

Since you don't know what "a number" is -- assign it to a variable:
Let n = the number

So, now instead of:
The difference of three times a number and 16 is at least 8.
We now have:
The difference of three times x and 16 is at least 8.

Breaking it up further:
The "difference of three times x and 16" is at least "8".
3x - 16 <= 8


18. Five less than the product of 6 and a number is no more than twice that same number.

Again, since you don't know what "a number" is assign it to a variable:
Let n = the number

When you see "product" -- think multiplication
When you see "is" -- think equal sign
When you see "no more than" -- think <

Putting it all together:
6x-5 <= 2x