Please help. me out with this question ​

Find the domain of the following expression: 1/(√x)-2

Sophia wrote an equation to represent the revenue of a movie theater for one day. she let x represent the number of child tickets sold and y represents the nunver of adult tickets sold. if a child ticket cost $4, an adult ticket cost $6, and the total revenue for the daybwas $420, which equation could sophia use to represent the number of chikd and adult tickets that were sold?

Miguel has 334 baseball cards and 278 football cards. he says, i have 612 cards in all. is that reasonable? explain using the words round and estimate.