36. What is the sum of the following integers (-12 + (+15+ (-18? a. 12 b. -13 c. -14 d. 14 37. what is the sum of two negative number? 39.what is the difference of number sentence (&14)-8-(12)? a-10 b.8 c.+10 d.-9 40.what is the value of (-15)-17-(20)? a. 14 b. 13 c.-12 d.-11