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Solve 10x + 9 = 99

The solution of 10x + 9 = 99 is x = 9.

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The lines y = 10x + 9 and y = 99 meet at x = 9468101214406080100120140160x = 9y = 10x + 9y = 99
The lines y = 10x + 9 and y = 99 meet at x = 9. 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=9910x + 9 = 99
  2. 2

    Subtract 9 from both sides:

    10x+9−9=99−9 ⇒ 10x=9010x + 9 - 9 = 99 - 9 \ \Rightarrow\ 10x = 90
  3. 3

    Divide both sides by 10:

    10x10=9010 ⇒ x=9\frac{10x}{10} = \frac{90}{10} \ \Rightarrow\ x = 9
  4. 4

    Check: put x = 9 back into the equation.

    10⋅9+9=90+9=99✓10\cdot9 + 9 = 90 + 9 = 99 \checkmark
LaTeX source of the formulas on this page
\[ 10x + 9 = 99\ \Rightarrow\ x = 9 \]
\[ 10x + 9 = 99 \]
\[ 10x + 9 - 9 = 99 - 9 \ \Rightarrow\ 10x = 90 \]
\[ \frac{10x}{10} = \frac{90}{10} \ \Rightarrow\ x = 9 \]
\[ 10\cdot9 + 9 = 90 + 9 = 99 \checkmark \]

Trying values of x in 10x + 9 = 99

x10x + 9Equals 99?
779no
889no
999yes
10109no
11119no

Questions

What is x in 10x + 9 = 99?

The solution of 10x + 9 = 99 is x = 9.

How do you solve 10x + 9 = 99?

Subtract 9 from both sides to get 10x = 90, then divide both sides by 10 to get x = 9.

How do I check the answer?

Replace x by 9: 10(9) + 9 = 99, which is 99.

Similar equations

    Solve 10x + 9 = 99: x = 9 (steps and check) | WordGPT