15.3. By how much does the sum of the first 15 positive odd integers exceed the sum of the first 10 positive even integers?
15.3. 115
We use the formula for the sum of an arithmetic series.
$$
\frac{15}{2}(2+14 \cdot 2)-\frac{10}{2}(4+9 \cdot 2)=15^{2}-10 \cdot 11=115
$$