A department store buys 300 shirts at a cost of 2,400 and sells them at a selling price of 10$ each. Find the percent markup

Carli has 90 apps on her phone. braylen has half the amount of apps as theiss. if carli has three timesthe amount of apps as theiss,how many apps does braylen have? let b represent the number of braylen's apps and t represent the number of theiss's apps.