Solve 12x − 15 = 225

The solution of 12x − 15 = 225 is x = 20.

12x - 15 = 225\ \Rightarrow\ x = 20

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The lines y = 12x − 15 and y = 225 meet at x = 20. 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.
$12x - 15 = 225$
2
Add 15 to both sides:
$12x - 15 + 15 = 225 + 15 \ \Rightarrow\ 12x = 240$
3
Divide both sides by 12:
$\frac{12x}{12} = \frac{240}{12} \ \Rightarrow\ x = 20$
4
Check: put x = 20 back into the equation.
$12\cdot20 - 15 = 240 - 15 = 225 \checkmark$

LaTeX source of the formulas on this page

\[ 12x - 15 = 225\ \Rightarrow\ x = 20 \]
\[ 12x - 15 = 225 \]
\[ 12x - 15 + 15 = 225 + 15 \ \Rightarrow\ 12x = 240 \]
\[ \frac{12x}{12} = \frac{240}{12} \ \Rightarrow\ x = 20 \]
\[ 12\cdot20 - 15 = 240 - 15 = 225 \checkmark \]

Trying values of x in 12x − 15 = 225

x	12x − 15	Equals 225?
18	201	no
19	213	no
20	225	yes
21	237	no
22	249	no

Questions

What is x in 12x − 15 = 225?

The solution of 12x − 15 = 225 is x = 20.

How do you solve 12x − 15 = 225?

Add 15 to both sides to get 12x = 240, then divide both sides by 12 to get x = 20.

How do I check the answer?

Replace x by 20: 12(20) − 15 = 225, which is 225.

Solve 12x − 15 = 225

How to work it out

Trying values of x in 12x − 15 = 225

Questions

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