I am on a computer.

I did that, but it didn't work.

Thanks. But I need to find the cost. But thanks.

Example 5) 2341-n=78

Thanks, Rose98. Or thanks, Madeline!

Example 3) y plus 31 equals 417

So, do I write the examples in word form?

Example 3) y+31=417

Example 2) n/5=45

Okay I will try to help. 

Example 1) =3(31n)

Definition below from a website so you can understand more.

Composite Number
A whole number that can be divided evenly by numbers other than 1 or itself. Example: 9 can be divided evenly by 3 (as well as 1 and 9), so 9 is a composite number. But 7 cannot be divided evenly (except by 1 and 7), so is NOT a composite number (it is a prime number). Whole numbers above 1 are either composite or prime.