Two artists are mixing up green paint for a mural. the first artist, shane, mixes 3 parts blue and 2 parts yellow to make a shade of green. the second artist, nora, mixes 5 parts blue and 3 parts yellow to make another shade of green. shane uses 24 ounces of yellow paint in his mixture. how many ounces of blue paint does he use? explain your reasoning

We would start by breaking down this problem. We want to know how much paint Shane used, so Nora isn't even relevant, we can just throw her out of the equation. Now we know that 2 parts of yellow paint was 24 ounces. We need to determine how much paint is in 1 part:
24/2 = 12
there is 12 ounces of paint in 1 part of paint.
Now what we need to figure out is how much blue paint was used. We know Shane used 3 parts of blue paint, and we know that 1 part = 12 ounces:
3*12 = 36

Shane used 36 ounces of blue paint

Hope this helps.