Idont know what these types of negative signs mean, i can't tell if it is just a negative number or something else..

-3+-4 = -7

Step-by-step explanation:

It is a negative number.

The negative in front of the 3 means you are short 3 of something.  The way I explain it.

You are short 3 dollars.  Then you borrow 4 dollars.  How much do you owe?

You owe $7 dollars.  -7

use formula for the circle a=3.14

step-by-step explanation:

1/800 is the right answer