If the two carts have the same speed, the total momentum of the system would be the sum of the momenta of the two carts. Since momentum is the product of mass and velocity, and the speed is the same for both carts, the total momentum would be twice the momentum of one of the carts.
Mathematically, if the momentum of each cart is represented by p, then the total momentum of the system, denoted as P_total, would be:
P_total = p + p = 2p.