Explain how you know which number 1 15/16 17/8 63/33 is closest to 2

I will say there are two ways to solve this problem. The first is, you can use your calculator and calculate it to see which is the closest to 2. The second way is divide it and here is how you do it:

1 is just 1
15/16      =        16 goes into 15 for less than one
17/8        =        8 goes into 17 for more than two so you can rewrite it                                            as 
63/33      =        33 does not go into 63 for two

So the answer is 17/8