120 glasses sold. 40% apple, 10% orange, 15% watermelon, the rest mixed.<br><br>
&bull; Percentage mixed = 100% − 40% − 10% − 15% = 35%<br>
&bull; Number of mixed juice glasses = 35% of 120 = \(\frac{35}{100} \times 120\) = 0.35 × 120 = 42<br><br>
Final Answer: 42