Algebra · real student question

Solve for x: (x - 1)/2 = 2 - (x + 2)/5.

Question

Solve for xx:

x12=2x+25.\frac{x-1}{2}=2-\frac{x+2}{5}.

Step-by-step solution

  1. Multiply every term by the LCD. The denominators are 22 and 55, so the least common denominator is 1010. Multiplying each term — including the standalone 22 — by 1010:

    10x12=10210x+25    5(x1)=202(x+2).10\cdot\frac{x-1}{2}=10\cdot 2-10\cdot\frac{x+2}{5}\;\Longrightarrow\;5(x-1)=20-2(x+2).

    Skipping the 10×2=2010\times2=20 is the error that most often derails this problem.

  2. Expand both sides. On the left, 5(x1)=5x55(x-1)=5x-5. On the right the bracket is subtracted, so both of its terms flip sign:

    202(x+2)=202x4=162x.20-2(x+2)=20-2x-4=16-2x.

    Writing 202x420-2x-4 before combining makes the sign of the 4-4 explicit; going straight to 162x16-2x in one jump is where a +4+4 tends to appear.

  3. Collect xx terms on one side. The equation is now 5x5=162x5x-5=16-2x. Adding 2x2x to both sides and adding 55:

    5x+2x=16+5    7x=21.5x+2x=16+5\;\Longrightarrow\;7x=21.

    Moving the 2x-2x to the left keeps the coefficient positive and avoids a division by a negative number.

  4. Divide and state the answer. Dividing both sides by 77:

    x=217=3.x=\frac{21}{7}=3.

  5. Check in the original equation. Left side: 312=1\frac{3-1}{2}=1. Right side: 23+25=21=12-\frac{3+2}{5}=2-1=1 ✓. Both sides equal 11, so x=3x=3 is correct — and checking in the original fractional form, not the cleared version, confirms the LCD step as well.

Answer

x=3x=3

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