hmm.. well you can't add them cause if the resistive force was equal to the downward forces, the dude would be hanging in midair... I don't have a very good explaination for this but think of it like this.. since the guy is falling downwards and there is no force pushing him downwards, so no force causing acceleration to make him go towards the ground except for gravity. Gravity is the only force providing accelertion... so shouldn't the accelerating force be 880N itself...? shouldn't the acceleration be 9.81m/s/s?
The logical answer is no, nothing falls with the acceleration of gravity in our world because of air resistance! Why is the accelerating force less than the weight ...because there's air resisting acting against weight! and hence decreasing the accelerating force... which technically is the same force as weight but it's being suppressed. So air resistance has to be the difference between weight and the accelerating force cause that's what come in betweeen them?
If I confused you further, really sorry..
i think if the forces equalled he would be travelling with constant velocity no?