<span>(4.214) x (3.06) = 12.89484 and can be rounded up to 12.9</span>

it just so happen that √2 is an irrational number, so any product with it as a factor, will yield an irrational number as well.
factoid: Ancient Greeks were scared of irrational numbers, and they steered clear from √2.
Answer:

Step-by-step explanation:
Let p represent cost of each drink.
We have been given that the medium pizza costs two times as much as one drink, so the cost of medium pizza would be
.
We are also told that the large pizza costs three times as much as one drink, so the cost of la pizza would be
.
We have been given that Mary wants to buy one large pizza, one medium pizza, and three drinks.
Since the cost of one drink is p, so cost of 3 three drinks would be
.
The total cost of one large pizza, one medium pizza, and three drinks would be 
Mary started with $30, so amount left after all of her purchases would be 30 minus total cost of all purchases.

Therefore, Mary will have
dollars left after making all of her purchases.