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Solve 6x + 9 = 129

The solution of 6x + 9 = 129 is x = 20.

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The lines y = 6x + 9 and y = 129 meet at x = 201416182022242690100110120130140150160170x = 20y = 6x + 9y = 129
The lines y = 6x + 9 and y = 129 meet at x = 20. 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.

    6x+9=1296x + 9 = 129
  2. 2

    Subtract 9 from both sides:

    6x+9−9=129−9 ⇒ 6x=1206x + 9 - 9 = 129 - 9 \ \Rightarrow\ 6x = 120
  3. 3

    Divide both sides by 6:

    6x6=1206 ⇒ x=20\frac{6x}{6} = \frac{120}{6} \ \Rightarrow\ x = 20
  4. 4

    Check: put x = 20 back into the equation.

    6⋅20+9=120+9=129✓6\cdot20 + 9 = 120 + 9 = 129 \checkmark
LaTeX source of the formulas on this page
\[ 6x + 9 = 129\ \Rightarrow\ x = 20 \]
\[ 6x + 9 = 129 \]
\[ 6x + 9 - 9 = 129 - 9 \ \Rightarrow\ 6x = 120 \]
\[ \frac{6x}{6} = \frac{120}{6} \ \Rightarrow\ x = 20 \]
\[ 6\cdot20 + 9 = 120 + 9 = 129 \checkmark \]

Trying values of x in 6x + 9 = 129

x6x + 9Equals 129?
18117no
19123no
20129yes
21135no
22141no

Questions

What is x in 6x + 9 = 129?

The solution of 6x + 9 = 129 is x = 20.

How do you solve 6x + 9 = 129?

Subtract 9 from both sides to get 6x = 120, then divide both sides by 6 to get x = 20.

How do I check the answer?

Replace x by 20: 6(20) + 9 = 129, which is 129.

Similar equations

    Solve 6x + 9 = 129: x = 20 (steps and check) | WordGPT