Algebra · real student question

Solve (350 + 6X)/16 = (450X - 6X)/9 for X.

Question

Solve for XX:

350+6X16=450X6X9\frac{350+6X}{16}=\frac{450X-6X}{9}

Step-by-step solution

  1. Simplify inside the numerators first. The right numerator has two like terms:

    450X6X=444X450X-6X=444X

    so the equation is

    350+6X16=444X9\frac{350+6X}{16}=\frac{444X}{9}

  2. Cross-multiply. Both denominators are nonzero constants, so multiply both sides by 169=14416\cdot 9=144:

    9(350+6X)=16(444X)9\left(350+6X\right)=16\left(444X\right)

  3. Expand both sides.

    3150+54X=7104X3150+54X=7104X

  4. Collect the XX-terms on one side. Subtracting 54X54X:

    3150=7050X3150=7050X

  5. Reduce the fraction to lowest terms — carefully. X=31507050X=\dfrac{3150}{7050}. Factoring, 3150=2325273150=2\cdot 3^{2}\cdot 5^{2}\cdot 7 and 7050=2352477050=2\cdot 3\cdot 5^{2}\cdot 47, so gcd=2352=150\gcd=2\cdot 3\cdot 5^{2}=150 and

    X=3150÷1507050÷150=21470.4468X=\frac{3150\div 150}{7050\div 150}=\frac{21}{47}\approx 0.4468

  6. Check both sides independently. With X=2147X=\dfrac{21}{47}: the left side is 350+126/4716=16576/4716=103647\dfrac{350+126/47}{16}=\dfrac{16576/47}{16}=\dfrac{1036}{47}, and the right side is 44421/479=9324/479=103647\dfrac{444\cdot 21/47}{9}=\dfrac{9324/47}{9}=\dfrac{1036}{47}. They match, so X=2147X=\dfrac{21}{47} is correct — note that a common wrong reduction of 31507050\dfrac{3150}{7050} to 7157\dfrac{7}{157} fails this check outright (21.8921.89 versus 2.202.20).

Answer

X=21470.4468X=\frac{21}{47}\approx 0.4468

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