Algebra · real student question

Solve the inequality x + 29 > 3x + 12.

Question

Solve

x+29>3x+12x+29>3x+12

Step-by-step solution

  1. Send the variable to the side with the larger coefficient. Subtracting xx from both sides leaves 3xx=2x3x-x=2x on the right, a positive coefficient:

    29>2x+1229>2x+12

  2. Move the constant. Subtract 1212 from both sides:

    17>2x17>2x

  3. Divide by 22 and keep the answer exact. 1717 is odd, so the boundary is genuinely fractional:

    172>xx<172=8.5\frac{17}{2}>x\quad\Longleftrightarrow\quad x<\frac{17}{2}=8.5

    Leaving it as 172\tfrac{17}{2} is preferable to rounding — here 8.58.5 happens to terminate, but the fraction is the exact form in general.

  4. Check integers straddling 8.58.5. At x=8x=8: left =37=37, right =36=36, and 37>3637>36 \checkmark. At x=9x=9: left =38=38, right =39=39, false \checkmark. At x=8.5x=8.5 both sides equal 37.537.5, so the strict inequality excludes the boundary. Solution set: (,172)\left(-\infty,\tfrac{17}{2}\right).

Answer

x<172,i.e. (,172)x<\frac{17}{2},\qquad\text{i.e. }\left(-\infty,\tfrac{17}{2}\right)

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