Question 142764
Mike has 19 coins (nickels, dimes and quarters) in his piggy bank with a total value of $2.35. There are 2 more dimes than nickels. How many of each type does Mike have? 
N+D+Q=19
5N+10D+25Q=235
?
Comment:
"There are 2 more dimes than nickels."
D = N+2
or
N -D -0 = -2
This is your 3rd equation 

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Fred, Tiger and Nancy play a round of golf together. Their combined score is 223. Fred’s score was 3 more than Nancy’s and Tiger’s score was 7 more than Fred’s. What was each person’s score. 
You would think something simple like
F=N+3
T=F+7
223=T+F+N 
But I need three equations with three unknown variables.
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T + F + N = 223
0 + F - N = 3
T - F + 0 = 7
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These are your three equations.
Cheers,
Stan H.