Answer:
First, here we must use the decimal notation for the percentages.
if we have a percentage x%, the decimal notation will be:
x%/100%.
Then for example, if x% = 90%.
the decimal notation will be:
90%/100% = 0.90
Data that we have:
90% order a meat entree, and 80% of these, order a drink.
So the percentage here that orders a drink is:
(0.9*0.8)*100% = 0.72*100% = 72%
10% order a vegetarian entree, and 40% of those order a drink, so the percentage here that orders a drink is:
0.1*0.4*100% = 0.04*100% = 4%.
Then the total percentage that orders drinks is 72% + 4% = 76%
76% of the customers that order an entree (meat or vegetarian) also order a drink.