Question 103236
A banana contains 3 more milligrams (mg) of calcium than an apple and 40 mg of calcium less than an orange. How much calcium is there in an orange if it contains the same amount as 5 apples and a banana. 
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banana = "b" ; apple = "a" ; orange = "r"
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EQUATIONS:
b = a+3
b = r-40
5a+ b =r
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Rearrange:
1a - 1b + 0r = -3
0a + 1b - 1r = -40
5a + 1b - 1r = 0
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Using a TI calculator I get:
a = 8 ; b = 11 ; r = 51
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Cheers,
Stan H.