Volume of a rectangular prism.. PLEASE HELP

[tex]\text {Volume = } \dfrac{5}{2x + 8} \times \dfrac{x+4}{4} \times \dfrac{12}{x} [/tex]

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Take out (x + 4) as a common factor :
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[tex]\text {Volume = } \dfrac{5}{2(x + 4)} \times \dfrac{x+4}{4} \times \dfrac{12}{x} [/tex]

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Cross out (x + 4) :
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[tex]\text {Volume = } \dfrac{5}{2} \times \dfrac{1}{4} \times \dfrac{12}{x} [/tex]

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Rewrite 12 as 4 x 3 :
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[tex]\text {Volume = } \dfrac{5}{2} \times \dfrac{1}{4} \times \dfrac{4 \times 3}{x} [/tex]

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Cross out 4 :
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[tex]\text {Volume = } \dfrac{5}{2} \times \dfrac{ 3}{x} [/tex]

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Combine into single fraction:
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[tex]\text {Volume = } \dfrac{15}{2x} [/tex]