in integers subtraction and addition are almost same ....
Addition :in addition if both numbers have different signs ..i.e - and + then we would find the difference and put the greater number sign ...For eg:(-6) + 12 =6 ...
if both are same ..i.e if both are either positive(+) or negative(-) then you add(or find the sum) and put the common sign ... For eg :+5+10 = +15 and (-5) + (-10) = (-5)]
Subtraction: in subtraction what you do is changing the sign of the second number ...and then depending upon the both signs follow the rules of addition ...
for eg: 6 - 4 ..it becomes 6 + (-4) ...so as they have different signs we can subtract them and put the greater number sign ...
i.e, 6 + (-4) = 2 ...
To find the sum follow these rules ......mentioned above ....
u can ask if you have any doubt ....
Hope it helps !!!