Solve 7x − 12 = 9

The solution of 7x − 12 = 9 is x = 3.

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

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

The lines y = 7x − 12 and y = 9 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.
$7x - 12 = 9$
2
Add 12 to both sides:
$7x - 12 + 12 = 9 + 12 \ \Rightarrow\ 7x = 21$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{21}{7} \ \Rightarrow\ x = 3$
4
Check: put x = 3 back into the equation.
$7\cdot3 - 12 = 21 - 12 = 9 \checkmark$

LaTeX source of the formulas on this page

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

Trying values of x in 7x − 12 = 9

x	7x − 12	Equals 9?
1	-5	no
2	2	no
3	9	yes
4	16	no
5	23	no

Questions

What is x in 7x − 12 = 9?

The solution of 7x − 12 = 9 is x = 3.

How do you solve 7x − 12 = 9?

Add 12 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) − 12 = 9, which is 9.

Solve 7x − 12 = 9

How to work it out

Trying values of x in 7x − 12 = 9

Questions

Similar equations