Ok here we are

reading carefully the stem ALWAYS when you deal with IR and also Verbal section of Gmat
Fort he first one Fb is 104 and apple 498. Roud the last one to 500. So 104 / 38 (the price of 1 IPO - by the way I do not know what is it but is not important so much) = 2.7. Then, 2.7 * 500 you roughfly have the same amount. So the answer is 183
Fo the second one onece again round the import of the first ten companies (alike of the remaining 19) and suddenly you can see that the sum of the 10 companies is MORE of the rest, combined.
Infact the answer are correct