What is the scale factor?

Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15

Mrs. blake's bill at a restaurant is $42.75. she wants to leave the waiter an 18% tip. how much will she pay in all, including the tip?

Afamily has two cars. the first car has a fuel efficiency of 25 miles per gallon of gas and the second has a fuel efficiency of 15 miles per gallon of gas. during one particular week, the two cars went a combined total of 1025 miles, for a total gas consumption of 55 gallons. how many gallons were consumed by each of the two cars that week?