There are 600 orders in total. Of those 600, we have 135+145 = 280 that are for lemonade or for orange juice. This means roughly 280/600 = 0.4667 of all the drinks are either lemonade or orange juice.
Assuming this ratio keeps up, we can multiply 0.4667 with 30 to get
30*0.4667 = 14.001 which rounds to 14
This represents the estimated number of drinks in the next 30 orders that are either lemonade or orange juice.
