3 + (-4) when you add or multiply or divide here are some things you should remember so you can understand it better
(-)(-) = +
(+)(-)= -
(+)(+)= +
(-)(+)= -
so now that you know this we can work on the equation
since there is a positive and a negative the answer has to be negative number and it automatically turns it to subtraction instead of addition so now its like this 3 - (-4) so now subtract 3 - 4 which is 1 but since the 4 is a negative then the answer goes to -1
hope i helped i just want to understand it so you can do this on your on next time
