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Solve 7x + 9 = 128

The solution of 7x + 9 = 128 is x = 17.

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The lines y = 7x + 9 and y = 128 meet at x = 1712141618202280100120140160x = 17y = 7x + 9y = 128
The lines y = 7x + 9 and y = 128 meet at x = 17. 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.

    7x+9=1287x + 9 = 128
  2. 2

    Subtract 9 from both sides:

    7x+9−9=128−9 ⇒ 7x=1197x + 9 - 9 = 128 - 9 \ \Rightarrow\ 7x = 119
  3. 3

    Divide both sides by 7:

    7x7=1197 ⇒ x=17\frac{7x}{7} = \frac{119}{7} \ \Rightarrow\ x = 17
  4. 4

    Check: put x = 17 back into the equation.

    7⋅17+9=119+9=128✓7\cdot17 + 9 = 119 + 9 = 128 \checkmark
LaTeX source of the formulas on this page
\[ 7x + 9 = 128\ \Rightarrow\ x = 17 \]
\[ 7x + 9 = 128 \]
\[ 7x + 9 - 9 = 128 - 9 \ \Rightarrow\ 7x = 119 \]
\[ \frac{7x}{7} = \frac{119}{7} \ \Rightarrow\ x = 17 \]
\[ 7\cdot17 + 9 = 119 + 9 = 128 \checkmark \]

Trying values of x in 7x + 9 = 128

x7x + 9Equals 128?
15114no
16121no
17128yes
18135no
19142no

Questions

What is x in 7x + 9 = 128?

The solution of 7x + 9 = 128 is x = 17.

How do you solve 7x + 9 = 128?

Subtract 9 from both sides to get 7x = 119, then divide both sides by 7 to get x = 17.

How do I check the answer?

Replace x by 17: 7(17) + 9 = 128, which is 128.

Similar equations

    Solve 7x + 9 = 128: x = 17 (steps and check) | WordGPT