Question 91631
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The three numbers: x, y, z
Write an equation for each statement:
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"The first of three numbers exceeds twice the second number by 4,"
x = 2y + 4
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"the third number is twice the first."
z = 2x
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"If the sum of the three numbers is 54,"
x + y + z = 54
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find the number.
Try to get everything in terms of y:
z = 2x
Substitute (2y+4) for x (1st equation)
z = 2(2y+4)
z = (4y + 8)
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In the 3rd equation substitute for x and z 
x + y + z = 54
(2y+4) + y + (4y+8)
7y + 12 = 54
7y = 54 - 12
7y = 42
y = 42/7
y = 6
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You should be able to find the values of x & z, using the above equation.
Check your solutions in the 3rd equation.
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Any questions?