Algebra · real student question

Solve for x: 14 = (108 + 84)/x.

Question

Solve for xx:

14=108+84x14=\frac{108+84}{x}

Step-by-step solution

  1. Simplify the numerator first. It contains no unknown:

    108+84=19214=192x108+84=192\qquad\Longrightarrow\qquad 14=\frac{192}{x}

    The domain restriction is x0x\neq0.

  2. Estimate before solving. The equation asks how many parts of size 1414 fit into 192192. Since 14×14=19614\times14=196 is slightly more than 192192, expect xx a little under 1414.

  3. Clear the denominator. Multiply both sides by xx:

    14x=19214x=192

  4. Divide by 14.

    x=19214x=\frac{192}{14}

  5. Reduce to lowest terms. Both 192192 and 1414 are even, so divide by 22:

    19214=967\frac{192}{14}=\frac{96}{7}

    Since 77 is prime and does not divide 9696, this is fully reduced. As a decimal, 967=13.71428513.714\tfrac{96}{7}=13.\overline{714285}\approx13.714 — just under 1414, as predicted ✓.

  6. Verify with exact arithmetic. 19296/7=192×796=134496=14\dfrac{192}{96/7}=192\times\dfrac{7}{96}=\dfrac{1344}{96}=14 ✓, matching the left side exactly.

Answer

x=19214=96713.714x=\frac{192}{14}=\frac{96}{7}\approx 13.714

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