<PRE><B>Question 582012</B>
My assignment was to collect data on 1 cup of broccoli and 1 cup of corn.
 The amount of calcium in one serving of broccoli is 62.4 mg and 1 mg of iron; in corn there is 5.4 mg of calcium and .6 mg of iron.
 The RDV for calcium a day is 1000 mg and for iron it is 18 mg.
 I need to construct and solve a linear system of two equations that would give me the amount of each food that would give me the full recommended values of calcium and iron
:
x = servings of broc
y = servings of corn
:
Calcium: 62.4x + 5.4y = 1000
:
Iron: 1x + .6y = 18
this equation is easy to arrange for substitution
x = (18-.6y)
:
Replace x with (18-.6y) in the calcium equation
62.4(18-.6y) + 5.4y = 1000
1123.2 - 37.44y + 5.4y = 1000
-32.04y = 1000 - 1123.2
y = {{{(-123.2)/(-32.04)}}}
y = +3.845 ~ 4 servings of corn
:
Find x
x = 18 - .6(3.845)
x = 15.692 ~ 16 servings of broc (ugh!)
:
:
See if that checks out for calcium
62.4(16) + 5.4(4) =
998 + 22 = 1020 mg, high because we rounded the servings up
:
You can check the iron requirement
16 + .6(4)
:
I think you went wrong because you did not write an equation for the iron requirement of 18 mg 
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