Solve 7x − 9 = 12

The solution of 7x − 9 = 12 is x = 3.

7x - 9 = 12\ \Rightarrow\ x = 3

Explain it step by step in chat Make a short video of it

The lines y = 7x − 9 and y = 12 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
The goal is to get x alone. Undo the operations in the opposite order: first the subtraction, then the multiplication.
$7x - 9 = 12$
2
Add 9 to both sides:
$7x - 9 + 9 = 12 + 9 \ \Rightarrow\ 7x = 21$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{21}{7} \ \Rightarrow\ x = 3$
4
Check: put x = 3 back into the equation.
$7\cdot3 - 9 = 21 - 9 = 12 \checkmark$

LaTeX source of the formulas on this page

\[ 7x - 9 = 12\ \Rightarrow\ x = 3 \]
\[ 7x - 9 = 12 \]
\[ 7x - 9 + 9 = 12 + 9 \ \Rightarrow\ 7x = 21 \]
\[ \frac{7x}{7} = \frac{21}{7} \ \Rightarrow\ x = 3 \]
\[ 7\cdot3 - 9 = 21 - 9 = 12 \checkmark \]

Trying values of x in 7x − 9 = 12

x	7x − 9	Equals 12?
1	-2	no
2	5	no
3	12	yes
4	19	no
5	26	no

Questions

What is x in 7x − 9 = 12?

The solution of 7x − 9 = 12 is x = 3.

How do you solve 7x − 9 = 12?

Add 9 to both sides to get 7x = 21, then divide both sides by 7 to get x = 3.

How do I check the answer?

Replace x by 3: 7(3) − 9 = 12, which is 12.

Solve 7x − 9 = 12

How to work it out

Trying values of x in 7x − 9 = 12

Questions

Similar equations