First you would need to find out how many 9 payments of 58$ would be and that is 522. Then you would need to subtract the 522 and the 480 and your answer would be 42$ so the interest would be 42$
This is not true. The infinite series

converges if and only if the sequence of its partial sums converges. The

-th partial sum is

but clearly this diverges as

gets arbitrarily large.
Even numbers can be divided into two equal groups while odd numbers cannot so every other number is an even number because it can be divided into two equal groups
Ratio for this mean for every 10 cats sold there was one dog
60/10 = ?
6 dogs
ratio = 60:6
2/3n (put that as a fraction) + 4 = 7