PLEASE HELLLP

One line passes through (-7,-4) and (5,4) . another line passes through the point (-4,6) and (6,-9)

What is the frequency of the sinusoidal graph?

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