This is Simple, Just Subtract Time taken by Science homework from time taken by Maths homework..
[tex] = 5 \frac{2}{15} - 2 \frac{13}{30} \\ = \frac{150}{15} - \frac{73}{30} \\ = \frac{300 - 73}{30} \\ = \frac{227}{30} \\ = 7 \frac{17}{30} \: hours \: more.[/tex]
!! Hope It Helps !!