What is the formula for the area of a circle?

How to solve a simultaneous equation involved with fractions?

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

Given: circle o, cd is diameter, chord ab || cd. arc ab = 74°, find arc ca.