Is 7,548,123 rational or irrational

What is the value of x when x + 7 = 21?

Which situation can be modeled by the inequality 5 + 10w ≥ 45? a. you start with $5 and save $10 a week until you have at least $45. b. you start with 5 baseball cards and purchase 10 cards every week until you have at most 45 cards. c. you start with 5 water bottles and purchases cases of 10 water bottles each until you have a total of 45 water bottles. d. you spend $5 plus $10 per week until you have less than $45.

Donald has x twenty-dollar bills and 11 ten-dollar bill. how much money does donald have? write your answer as an expression.