A 12-oz cup of regular coffee at Starbucks has 13 times the amount of caffeine found in the same-sized serving of decaffeinated coffee. Together they contain 280 mg of caffeine. How much caffeine is in each type of coffee?

If the decaffeinated is x, the regular coffee would be 13*x = 13x

They both total 280 mg.

x + 13x = 280

14x + 280

x = 280/14

x = 20 mg

x, and 13x x = 20, 13x = 13*20 = 260

Decaffeinated has 20 mg and the regular coffee in Starbucks has 260 mg.