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Solve 2x + 5 = 21

The solution of 2x + 5 = 21 is x = 8.

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The lines y = 2x + 5 and y = 21 meet at x = 82468101214101520253035x = 8y = 2x + 5y = 21
The lines y = 2x + 5 and y = 21 meet at x = 8. 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+5=212x + 5 = 21
  2. 2

    Subtract 5 from both sides:

    2x+5−5=21−5 ⇒ 2x=162x + 5 - 5 = 21 - 5 \ \Rightarrow\ 2x = 16
  3. 3

    Divide both sides by 2:

    2x2=162 ⇒ x=8\frac{2x}{2} = \frac{16}{2} \ \Rightarrow\ x = 8
  4. 4

    Check: put x = 8 back into the equation.

    2⋅8+5=16+5=21✓2\cdot8 + 5 = 16 + 5 = 21 \checkmark
LaTeX source of the formulas on this page
\[ 2x + 5 = 21\ \Rightarrow\ x = 8 \]
\[ 2x + 5 = 21 \]
\[ 2x + 5 - 5 = 21 - 5 \ \Rightarrow\ 2x = 16 \]
\[ \frac{2x}{2} = \frac{16}{2} \ \Rightarrow\ x = 8 \]
\[ 2\cdot8 + 5 = 16 + 5 = 21 \checkmark \]

Trying values of x in 2x + 5 = 21

x2x + 5Equals 21?
617no
719no
821yes
923no
1025no

Questions

What is x in 2x + 5 = 21?

The solution of 2x + 5 = 21 is x = 8.

How do you solve 2x + 5 = 21?

Subtract 5 from both sides to get 2x = 16, then divide both sides by 2 to get x = 8.

How do I check the answer?

Replace x by 8: 2(8) + 5 = 21, which is 21.

Similar equations

    Solve 2x + 5 = 21: x = 8 (steps and check) | WordGPT