Write a rule for the nth term of the arithmetic sequence a2=-28, a20=52 The answer is aN= -332/9 + 40/9N if that helps.

arithmetic sequences work a lot like lines 


a2=-28, a20=52 


tells us that 
d=(52-28)/(20-2)=4/3 


then using the "points" we can write the general term 
an = am +(n-m)d (n > m) 
an = -28+(n-2)*(4/3)