Azul bought 10 reams of paper at the store for a total of $84. the tax on the purchase was four dollars what was the cost of each ream of paper. which equation could be used to represent this situation

One cell phone plan charges $20 per month plus $0.15 per minute used. a second cell phone plan charges $35 per month plus $0.10 per minute used. write and solve an equation to find the number of minutes you must talk to have the same cost for both calling plans.