Find the next two terms for each sequence. then write its recursive formula 6, 7, 7.5, 7.75

For each term you're adding half of what you added before. 
So the fifth term is 7.75 + 1/8 = 7.875
the sixth term is 7.875 + 1/16 = 7.9375

a_1 = 6
a_2 = 6 + 1 = 7   =   a_1 + 1 =  a_1 + (½)^0
a_3 = 7 + ½ = 7.5  =   a_2 + ½   = a_2 + (½)^1
a_4 = 7.5 + ¼ = 7.75   =  a_3 + ¼  =  a_3 + (½)^2

So each power of ½ is (n - 2).  The recursive formula is

8,400-6,400=xx/6,400anyways the percent increase is 31.25% or 0.3125 you can round if you can