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Solve 3x + 9 = 42

The solution of 3x + 9 = 42 is x = 11.

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The lines y = 3x + 9 and y = 42 meet at x = 1168101214162530354045505560x = 11y = 3x + 9y = 42
The lines y = 3x + 9 and y = 42 meet at x = 11. 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.

    3x+9=423x + 9 = 42
  2. 2

    Subtract 9 from both sides:

    3x+9−9=42−9 ⇒ 3x=333x + 9 - 9 = 42 - 9 \ \Rightarrow\ 3x = 33
  3. 3

    Divide both sides by 3:

    3x3=333 ⇒ x=11\frac{3x}{3} = \frac{33}{3} \ \Rightarrow\ x = 11
  4. 4

    Check: put x = 11 back into the equation.

    3⋅11+9=33+9=42✓3\cdot11 + 9 = 33 + 9 = 42 \checkmark
LaTeX source of the formulas on this page
\[ 3x + 9 = 42\ \Rightarrow\ x = 11 \]
\[ 3x + 9 = 42 \]
\[ 3x + 9 - 9 = 42 - 9 \ \Rightarrow\ 3x = 33 \]
\[ \frac{3x}{3} = \frac{33}{3} \ \Rightarrow\ x = 11 \]
\[ 3\cdot11 + 9 = 33 + 9 = 42 \checkmark \]

Trying values of x in 3x + 9 = 42

x3x + 9Equals 42?
936no
1039no
1142yes
1245no
1348no

Questions

What is x in 3x + 9 = 42?

The solution of 3x + 9 = 42 is x = 11.

How do you solve 3x + 9 = 42?

Subtract 9 from both sides to get 3x = 33, then divide both sides by 3 to get x = 11.

How do I check the answer?

Replace x by 11: 3(11) + 9 = 42, which is 42.

Similar equations

    Solve 3x + 9 = 42: x = 11 (steps and check) | WordGPT