Find the missing number: 70, 102, ?, 178, 222

Which simplifys to a+ b? a-(1-b)+1 -(1-a)-b+1 (a--1) -1)+1

If the ratio of sum of the first m and n terms of an ap is m2 : n2 , show that the ratio of its mth and nth terms is (2m − 1) : (2n − 1).

How many sides does a regular polygon have if each exterior angle measure is 45 degrees explain your answer, i really don't understand this.