What is 2 x 5/8 please and thank you

Volume of cylinder with a radius of 8cm and height of 25 cm

Which best explains why this triangle is or is not a right triangle?

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. when the check comes, it says they also need to pay $3.99 in sales tax. what percentage of the subtotal is the sales tax