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Solve 2x + 3 = 21

The solution of 2x + 3 = 21 is x = 9.

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The lines y = 2x + 3 and y = 21 meet at x = 9468101214101520253035x = 9y = 2x + 3y = 21
The lines y = 2x + 3 and y = 21 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.

    2x+3=212x + 3 = 21
  2. 2

    Subtract 3 from both sides:

    2x+3−3=21−3 ⇒ 2x=182x + 3 - 3 = 21 - 3 \ \Rightarrow\ 2x = 18
  3. 3

    Divide both sides by 2:

    2x2=182 ⇒ x=9\frac{2x}{2} = \frac{18}{2} \ \Rightarrow\ x = 9
  4. 4

    Check: put x = 9 back into the equation.

    2⋅9+3=18+3=21✓2\cdot9 + 3 = 18 + 3 = 21 \checkmark
LaTeX source of the formulas on this page
\[ 2x + 3 = 21\ \Rightarrow\ x = 9 \]
\[ 2x + 3 = 21 \]
\[ 2x + 3 - 3 = 21 - 3 \ \Rightarrow\ 2x = 18 \]
\[ \frac{2x}{2} = \frac{18}{2} \ \Rightarrow\ x = 9 \]
\[ 2\cdot9 + 3 = 18 + 3 = 21 \checkmark \]

Trying values of x in 2x + 3 = 21

x2x + 3Equals 21?
717no
819no
921yes
1023no
1125no

Questions

What is x in 2x + 3 = 21?

The solution of 2x + 3 = 21 is x = 9.

How do you solve 2x + 3 = 21?

Subtract 3 from both sides to get 2x = 18, then divide both sides by 2 to get x = 9.

How do I check the answer?

Replace x by 9: 2(9) + 3 = 21, which is 21.

Similar equations

    Solve 2x + 3 = 21: x = 9 (steps and check) | WordGPT