Question 1065896

Let A = number of 1-peso coins
Let B = number of 5-peso coins
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A+5B = 80      (1)
A+B = 20        (2)

(1)-(2) :
0A + 4B = 60
           B = 60/4 = 15,  so 15 5-peso coins
   B=15 —> A=20-15=5, so 5 1-peso coins
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Ans:   15 five-peso coins and  5 one-peso coins

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Check:   15 + 5 = 20 (ok)
          5(15) + 5(1) = 75 + 5 = 80  (ok)