Write a system of equations to describe the situation below, solve, and fill in the blanks. Carly, an office manager, needs to find a courier to deliver a package. The first courier she is considering charges a fee of $13 plus $3 per kilogram. The second charges $5 plus $4 per kilogram. Carly determines that, given her package's weight, the two courier services are equivalent in terms of cost. What is the weight? How much will it cost?

At a package weight of kilograms, the two couriers both cost $