Which of the following is a logarithmic function?

What is the value of x in the this question ?

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

The cost of using a service is $0.25 per min. what equation correctly represents the total cost c, in dollars, for d days of use?