Can you ever use a calculator to determine if a number is rational or irrational

Does anyone know how to do geometryme with this problem

Jada has a meal in a restaurant she adds up the prices listed on the menu for everything they ordered and gets a subtotal of $42.00. after tax the total is 45.99. what percentage of the subtotal is the total?

Tatiana reads 40 pages of her book every night for x number of nights. write an expression that shows the number of pages she has read