What is the probability of randomly choosing a silver tack or a white tack from a box that contains only 15 blue tacks 5 red tacks 20 white tacks and 8 silver tacks?

If there are 48 tacks, (15+5+20+8), you want to divide the number of one color over the total to find the percentage of that color out of the whole.

If there are 8 silver tacks, take 8 over 48, which equals .167.If there are 20 white tacks, take 20 over 48, which equals .4167

Now you know the percentage of silver out of the whole, and the percentage of white out of the whole.

To figure out the white and silver together, add them together!
White and Silver tacks make up about .583, or 58.3%

And that's your answer. You have a 58% chance of picking a white or silver tack from the box when picked at random.