so another thing is that I don't know if it was a typo on the last graph or if I just misunderstood, because it said 2 sub 1, for instance, was 2. But, I'm pretty sure it should just be 1, since there's only one way for a one digit number to end in 2. Also, the equation said that 7sub(i+1) = 2*(2 sub i). But, it said 7 sub 2 = 2, but according to the equation it should be 2*2=4. I thought maybe they included they're symmetrical pairs, like 2 sub i on the graph included 2 sub i plus 8 sub i, but that was definitely not the case according to the solution.