For #17, can somebody tell me how to do this?

Step-by-step explanation:  

you have to add all the sides together and then divied by two on the first 4 and then on the next two your going to have too find the numbers for each side dy multiplying and then add the side and then divied by too

-7/8

step-by-step explanation:

instead of subtracting you add the -6/8 and -1/8

the workers who do no drive has no reasonable reason to buy gasoline due to they don't have anything to use it for