As given, the old load is 2800 watts and the new load is \(10(150)+6(100)=1500+600=2100\) watts. So, the fraction that represents a comparison of the new load with the old load is:

\(\displaystyle\frac{{2100}}{{2800}}=\frac{{{700}\cdot{3}}}{{{700}\cdot{4}}}=\frac{{3}}{{4}}\)