How do know when to add or subtract integers

It really depends on the sign in front of the numbers for that given example though -68-1 +(-6) you would have to add the -68 and -1 since they are both negative and then you would have to add it again to the -6 since they also have the same sign. Therefore the answer would be -75

the formula of a slope:

we have the points (-2, 7) and (2, 3). substitute: