Solve 9x − 15 = 102

The solution of 9x − 15 = 102 is x = 13.

9x - 15 = 102\ \Rightarrow\ x = 13

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The lines y = 9x − 15 and y = 102 meet at x = 13. The solution of the equation is the x-coordinate of the point where the two sides are equal.

How to work it out

1
The goal is to get x alone. Undo the operations in the opposite order: first the subtraction, then the multiplication.
$9x - 15 = 102$
2
Add 15 to both sides:
$9x - 15 + 15 = 102 + 15 \ \Rightarrow\ 9x = 117$
3
Divide both sides by 9:
$\frac{9x}{9} = \frac{117}{9} \ \Rightarrow\ x = 13$
4
Check: put x = 13 back into the equation.
$9\cdot13 - 15 = 117 - 15 = 102 \checkmark$

LaTeX source of the formulas on this page

\[ 9x - 15 = 102\ \Rightarrow\ x = 13 \]
\[ 9x - 15 = 102 \]
\[ 9x - 15 + 15 = 102 + 15 \ \Rightarrow\ 9x = 117 \]
\[ \frac{9x}{9} = \frac{117}{9} \ \Rightarrow\ x = 13 \]
\[ 9\cdot13 - 15 = 117 - 15 = 102 \checkmark \]

Trying values of x in 9x − 15 = 102

x	9x − 15	Equals 102?
11	84	no
12	93	no
13	102	yes
14	111	no
15	120	no

Questions

What is x in 9x − 15 = 102?

The solution of 9x − 15 = 102 is x = 13.

How do you solve 9x − 15 = 102?

Add 15 to both sides to get 9x = 117, then divide both sides by 9 to get x = 13.

How do I check the answer?

Replace x by 13: 9(13) − 15 = 102, which is 102.

Solve 9x − 15 = 102

How to work it out

Trying values of x in 9x − 15 = 102

Questions

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