To solve this problem, we must figure out what 30% of $85 is. To do this, we must first convert 30% to its decimal equivalent. We divide 30/100 to find the decimal because percentages are portions of 100.
30/100 = 0.3
Next, we must multiply this decimal by $85. We do this because the word "of" in mathematics implies that we must use multiplication.
0.3 * 85 = 25.5
Therefore, Aubrey tips the waitstaff $25.50.
Hope this helps!