First, subtract 18 from 21.96.
21.96 - 18 = 3.96
That is the amount it was increased by.
Now, to find the percent increase, divide 3.96 by 18.
3.96 ÷ 18 = 0.21444
In percents, that is equal to 21.444%.
The large fruit smoothie is 21.444% larger.
Hope this helps!