Thank you all for the information.
But I still think I'm going to stumble a little upon number-crunchings,
things like wavelength = 550 nm, and trying to find the inverse for it...
For example... for the problem #62, I had to do 1.6/6400 X10^-19,
and got the right answer. I guess supposedly, all you need to know
is that 1.6/6400 can be easily calculated by deducing it to the ratio of1/4?