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Solve 2x + 15 = 21

The solution of 2x + 15 = 21 is x = 3.

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The lines y = 2x + 15 and y = 21 meet at x = 3-22468101520253035x = 3y = 2x + 15y = 21
The lines y = 2x + 15 and y = 21 meet at x = 3. 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+15=212x + 15 = 21
  2. 2

    Subtract 15 from both sides:

    2x+15−15=21−15 ⇒ 2x=62x + 15 - 15 = 21 - 15 \ \Rightarrow\ 2x = 6
  3. 3

    Divide both sides by 2:

    2x2=62 ⇒ x=3\frac{2x}{2} = \frac{6}{2} \ \Rightarrow\ x = 3
  4. 4

    Check: put x = 3 back into the equation.

    2⋅3+15=6+15=21✓2\cdot3 + 15 = 6 + 15 = 21 \checkmark
LaTeX source of the formulas on this page
\[ 2x + 15 = 21\ \Rightarrow\ x = 3 \]
\[ 2x + 15 = 21 \]
\[ 2x + 15 - 15 = 21 - 15 \ \Rightarrow\ 2x = 6 \]
\[ \frac{2x}{2} = \frac{6}{2} \ \Rightarrow\ x = 3 \]
\[ 2\cdot3 + 15 = 6 + 15 = 21 \checkmark \]

Trying values of x in 2x + 15 = 21

x2x + 15Equals 21?
117no
219no
321yes
423no
525no

Questions

What is x in 2x + 15 = 21?

The solution of 2x + 15 = 21 is x = 3.

How do you solve 2x + 15 = 21?

Subtract 15 from both sides to get 2x = 6, then divide both sides by 2 to get x = 3.

How do I check the answer?

Replace x by 3: 2(3) + 15 = 21, which is 21.

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    Solve 2x + 15 = 21: x = 3 (steps and check) | WordGPT