Jackie purchased 4 cupcakes for $4.50 each. there was a 10% sales tax on her total order. how much did she pay for her order?

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.