Help with molar ratio
The whole point of this problem is that for each 100 molecules of annealed oligos, you need to have one molecule of each fragment. 

You need to take into account the following:

The MW of each fragment is approximately proportional to the length of the fragment. Thus if you divide the concentration by the length of each fragment, you can get a value that simulates the molarity, meaning that you can use these values to fix to the ratio that you are asked between the different fragments.

For example, if the fragment1 is 100 bp and you have 10ng/µl, fragment2 is 200 bp with the same concentration, then you need to add 1 volume of fragment1 and 2 volumes of fragment2 to get the 1:1 molar ration.

In a similar way, you can calculate the amount of oligos added to have 100x more (of the ratio of concentration to bp length) than the respective fragments.