John has 21 paper bills consisting of $20, $50, $100. He has twice as many $50 bills as $20 bills and has a total amount of 1380. How many of each type of bill does John have? x = number of $20 bills 2x = number of $50 bills {he has twice as many $50 bills as $20 bills} 21  3x = number of $100 bills {total number of bills minus $20 and $50 bills} 20x + 50(2x) + 100(21  3x) = 1380 {value of bill times number of bills equals total value} 20x + 100x + 2100  300x = 1380 {used distributive property} 180x + 2100 = 1380 {combined like terms} 180x = 720 {subtracted 2100 from each side} x = 4 $20 bills {divided each side by 180} 2x = 8 $50 bills {substituted 4, in for x, into 2x} 21  3x = 9 $100 bills {substituted 4, in for x, into 21  3x} John has 4  $20 bills, 8  $50 bills, and 9  $100 bills  Algebra House
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