Question 898302
Suppose that Maria has 130 coins consisting of pennies, nickels, and dimes. The number of nickels she has is 40 less than twice the number of pennies; the number of dimes she has is 10 less than three times the number of pennies. How many coins of each kind does she have? 
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let x=number of pennies
2x-40=number of nickels
3x-10=number of dimes
...
x+(2x-40)+(3x-10)=130
x+2x-40+3x-10=130
6x=180
x=30
2x-40=60-40=20
3x-10=90-10=80
number of pennies=30
number of nickels=20
number of dimes=80