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Solve 10x + 9 = 129

The solution of 10x + 9 = 129 is x = 12.

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The lines y = 10x + 9 and y = 129 meet at x = 126810121416186080100120140160180200x = 12y = 10x + 9y = 129
The lines y = 10x + 9 and y = 129 meet at x = 12. 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.

    10x+9=12910x + 9 = 129
  2. 2

    Subtract 9 from both sides:

    10x+9−9=129−9 ⇒ 10x=12010x + 9 - 9 = 129 - 9 \ \Rightarrow\ 10x = 120
  3. 3

    Divide both sides by 10:

    10x10=12010 ⇒ x=12\frac{10x}{10} = \frac{120}{10} \ \Rightarrow\ x = 12
  4. 4

    Check: put x = 12 back into the equation.

    10⋅12+9=120+9=129✓10\cdot12 + 9 = 120 + 9 = 129 \checkmark
LaTeX source of the formulas on this page
\[ 10x + 9 = 129\ \Rightarrow\ x = 12 \]
\[ 10x + 9 = 129 \]
\[ 10x + 9 - 9 = 129 - 9 \ \Rightarrow\ 10x = 120 \]
\[ \frac{10x}{10} = \frac{120}{10} \ \Rightarrow\ x = 12 \]
\[ 10\cdot12 + 9 = 120 + 9 = 129 \checkmark \]

Trying values of x in 10x + 9 = 129

x10x + 9Equals 129?
10109no
11119no
12129yes
13139no
14149no

Questions

What is x in 10x + 9 = 129?

The solution of 10x + 9 = 129 is x = 12.

How do you solve 10x + 9 = 129?

Subtract 9 from both sides to get 10x = 120, then divide both sides by 10 to get x = 12.

How do I check the answer?

Replace x by 12: 10(12) + 9 = 129, which is 129.

Similar equations

    Solve 10x + 9 = 129: x = 12 (steps and check) | WordGPT