Answer :

To multiply a pair of integers if both numbers have the same sign, their product is the product of their absolute values (their product is positive). If the numbers have opposite signs, their product is the opposite of the product of their absolute values (their product is negative).
Integer Numbers -They are all positive and negative whole numbers, which do not include any fractional or decimal part.  

Consist of the set of numbers: {…-4, -3, -2, -1, 0, 1, 2, 3, 4…} 

If a number has no sign it usually means that it is a positive number. 
 
                           Adding and Subtracting integers 

             Adding integers

(+)+(+) = + sum

(-)+(-) = - sum  

(+)+(-) or (-)+(+) = difference of numbers with signs of larger number in absolute value. 

           Subtracting Integers

(-)(-) = + sum 

(-)(+) = - sum