Rohan and Sim are building a terrarium. The first layer is made of sand. They can use a scoop to add sand to make the first layer. Rohan has a 1/3-cup scoop and Sim has a 1/4-cup scoop.

Write and solve an equation to model the number of scoops needed to fill the first layer if only Rohan's scoop is used. How many scoops are needed?​