A portfolio consists of 120 shares of Atlas stock which sells for $50
per share and 150 shares of Babcock stock which sell for $20 per
share. What are the weights of the two stocks in this portfolio?

Hello.

Here's a good summary of the meaning of "porfolio weights":

"Portfolios are groups of assets, such as stocks and bonds, that are
held by an investor.
One convenient way to describe a portfolio is by listing the
proportion of the total value of the portfolio that is invested into
each asset.
These proportions are called portfolio weights."
source: Oregon State - Finance Powerpoint
http://classes.bus.oregonstate.edu/ba442/CJed3.Chapter11.ppt

Also see:

" An asset?s investment weight is simply the fraction of the portfolio
represented by the asset."
http://www.bnet.fordham.edu/blake/portrisk.pdf


With this in mind...

120 shares of Atlas stock at $50 per share has a value of $6000 (i.e.,
120 shares * $50/share = $6000).

150 shares of Babcock stock at $20 per share has a value of $3000
(i.e., 150 shares * $20/share = $3000).

The total value of the portfolio is $9000 (i.e., $6000 + $3000 = $9000).

So...

The Atlas stock's portfolio weight is 2/3 or .667 or 66.7% (i.e., $6000/$9000).

The Babcock stock's weight is 1/3 or .333 or 33.3% (i.e., $3000/$9000).

I hope this helps.