What you do is divide the sum by 2. You will come out with and answer of 1891. Now, to figure out the years they were invented you take the difference of 192 and divide that in half also. It will come out to 96. Now, you subtract 1891 by 96 and that is the year the pencil was invented (1795=pencil) now with the other half (1891) you add on 96 and you’ll come out with the answer of 1987.
