Question 645379
A girl saves $1 and $2 coins. She takes it to a bank, she has 180 coins in total that equals $260. Use simultaneous equations to work out how many $1 and $2 coins there are. 
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Let x = number of $1 coins
y = number of $2 coins
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from:"she has 180 coins" we get equation 1:
x+y = 180
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from:"total that equals $260" we get equation 2:
x + 2y = 260
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solve equation 1 for y:
x+y = 180
y = 180-x
substitute above into equation 2:
x+y = 180
x + 2(180-x) = 260
x + 360-2x = 260
360-x = 260
-x = -100
x = 100 (number of $1 coins)
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Number of $2 coins:
x+y = 180
100+y = 180
y = 80