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Solve 12x + 9 = 81

The solution of 12x + 9 = 81 is x = 6.

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The lines y = 12x + 9 and y = 81 meet at x = 62468101220406080100120140160x = 6y = 12x + 9y = 81
The lines y = 12x + 9 and y = 81 meet at x = 6. The solution of the equation is the x-coordinate of the point where the two sides are equal.

How to work it out

  1. 1

    The goal is to get x alone. Undo the operations in the opposite order: first the addition, then the multiplication.

    12x+9=8112x + 9 = 81
  2. 2

    Subtract 9 from both sides:

    12x+9−9=81−9 ⇒ 12x=7212x + 9 - 9 = 81 - 9 \ \Rightarrow\ 12x = 72
  3. 3

    Divide both sides by 12:

    12x12=7212 ⇒ x=6\frac{12x}{12} = \frac{72}{12} \ \Rightarrow\ x = 6
  4. 4

    Check: put x = 6 back into the equation.

    12⋅6+9=72+9=81✓12\cdot6 + 9 = 72 + 9 = 81 \checkmark
LaTeX source of the formulas on this page
\[ 12x + 9 = 81\ \Rightarrow\ x = 6 \]
\[ 12x + 9 = 81 \]
\[ 12x + 9 - 9 = 81 - 9 \ \Rightarrow\ 12x = 72 \]
\[ \frac{12x}{12} = \frac{72}{12} \ \Rightarrow\ x = 6 \]
\[ 12\cdot6 + 9 = 72 + 9 = 81 \checkmark \]

Trying values of x in 12x + 9 = 81

x12x + 9Equals 81?
457no
569no
681yes
793no
8105no

Questions

What is x in 12x + 9 = 81?

The solution of 12x + 9 = 81 is x = 6.

How do you solve 12x + 9 = 81?

Subtract 9 from both sides to get 12x = 72, then divide both sides by 12 to get x = 6.

How do I check the answer?

Replace x by 6: 12(6) + 9 = 81, which is 81.

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    Solve 12x + 9 = 81: x = 6 (steps and check) | WordGPT