Write a system of equations to describe the situation below, solve using any method, and fill in the blanks. Nicole and Josie are both selling cookie dough for a fundraiser. Although Nicole has already sold 4 tubs, Josie hasn't sold any yet. If Nicole starts selling 5 tubs per day and Josie begins selling 6 tubs per day, they will eventually sell the same amount of cookie dough. How many tubs will each sell? How many days will that take?