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Solve 9x + 15 = 87

The solution of 9x + 15 = 87 is x = 8.

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The lines y = 9x + 15 and y = 87 meet at x = 82468101214406080100120140x = 8y = 9x + 15y = 87
The lines y = 9x + 15 and y = 87 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.

    9x+15=879x + 15 = 87
  2. 2

    Subtract 15 from both sides:

    9x+15−15=87−15 ⇒ 9x=729x + 15 - 15 = 87 - 15 \ \Rightarrow\ 9x = 72
  3. 3

    Divide both sides by 9:

    9x9=729 ⇒ x=8\frac{9x}{9} = \frac{72}{9} \ \Rightarrow\ x = 8
  4. 4

    Check: put x = 8 back into the equation.

    9⋅8+15=72+15=87✓9\cdot8 + 15 = 72 + 15 = 87 \checkmark
LaTeX source of the formulas on this page
\[ 9x + 15 = 87\ \Rightarrow\ x = 8 \]
\[ 9x + 15 = 87 \]
\[ 9x + 15 - 15 = 87 - 15 \ \Rightarrow\ 9x = 72 \]
\[ \frac{9x}{9} = \frac{72}{9} \ \Rightarrow\ x = 8 \]
\[ 9\cdot8 + 15 = 72 + 15 = 87 \checkmark \]

Trying values of x in 9x + 15 = 87

x9x + 15Equals 87?
669no
778no
887yes
996no
10105no

Questions

What is x in 9x + 15 = 87?

The solution of 9x + 15 = 87 is x = 8.

How do you solve 9x + 15 = 87?

Subtract 15 from both sides to get 9x = 72, then divide both sides by 9 to get x = 8.

How do I check the answer?

Replace x by 8: 9(8) + 15 = 87, which is 87.

Similar equations

    Solve 9x + 15 = 87: x = 8 (steps and check) | WordGPT