An artist uses 3 ounces of paint for every large canvas they cover, and 2 ounces of paint for every small canvas they cover.  They have completed 3 large paintings and 4 small paintings.  How many ounces of paint have they used? Let's think first. Chain of thought:
The large paintings have used 3 * 3 = 9 ounces. The small paintings have used 2 * 4 = 8 ounces. In total, all the paintings have used 9  + 8 = 17 ounces.
Therefore, the answer is 17.