Question

What is the value of x in the equation 4x + 8y = 40, when y = 0.8?

Answer 1

4x + 8y = 40 

When y = 0.8
4x + 8(0.8) = 40
4x + 6.4 = 40
4x = 40 - 6.4
4x = 33.6
x = 8.4

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Answer: x = 8.4
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Answer 2

To find your answer you must substitute y for 0.8
4x + (8)(0.8) = 40
Now solve for x
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SOLVING...

4x + (8)(0.8) = 40
4x + 6.4 = 40

Subtract 6.4 from each side
4x+ 6.4 − 6.4 = 40 − 6.4
4x = 33.6

Divide each side by 4
4x ÷ 4 = 33.6 ÷ 4
x = 8.4