Find the common difference of the arithmetic sequence. 6.5,5, 3.5, 2, ...

The common difference is?

An arithmetic series a consists of consecutive integers that are multiples of 4 what is the sum of the first 9 terms of this sequence if the first term is 0

With both problems. a.s.a.p directions on photo ^

Jonathan can type 20 documents in 40 minutes ,and susan can type it in 30 minutes and jack can type it in 24 minutes working together ,how much time will it is take them type the same document