Please, I'm having issues with number 4 and 5​

What is the solution to the system of the equations? x = y - 3 x + 3y = 13

In the diagram, a building cast a 35-ft shadow and a flagpole casts an 8-ft shadow. if the the flagpole is 18 ft tall, how tall is the building? round the the nearest tenth.

Ashley spent half of her lunch money on a turkey sandwich. then she spent two-thirds of the money she had left on a bottle of juice and the rest of the money on a cookie. if the cookie cost $.75, how much lunch money did ashley have to start with?