Find the fraction of the original rice remaining after each day.
\\(\begin{aligned}
\text{After Day 1 (15\% used)} &: 85\% \text{ remaining}
\\
\text{Day 2: 20\% of remainder used} &= 0.20 \times 85\% = 17\% \text{ of original}
\\
\text{Total used} &= 15\% + 17\% = 32\%
\\
\text{Not used} &= 100\% - 32\% = 68\%
\end{aligned}\\)
Final Answer: 68%