## Elementary Technical Mathematics

(a) Sum: $-13$ (b) Difference: $3$ (c) Product: $40$
RECALL: (1) For any real number $a$, $a + 0 = a$. (2) For any real number $a$, $a(0) = 0$. (3) $a-b=a+(-b)$. (4) The product of two integers with the same sign is positive. (5) The sum of two negative numbers is negative. (6) The sum of two positive numbers is positive. (7) The sum of two numbers with different signs is equal to the difference of their absolute values. The sum will have the same sign as the number with the bigger absolute value. Thus, the sum, difference, and product of the given expressions are: (a) Sum: $(-5) + (-8) = -13$ (b) Difference: $(-5) - (-8) = (-5) + (8) = |8|-|-5|=8-5=3$ (c) Product: $(-5)(-8) = 40$