Can you please help me with a , b & c .

Can someone me and plz do the problem

If the sales price of a dvd is $20 and the markup is 34%, what is the cost of the dvd?

The sum of the first eight terms of an arithmetic progression is 9m + 14. the fifth term of the06 progression is 2m - 6, where m is a constant.given that the first term of the progression is 26,find the value of the common difference, d and thevalue of m.