Solve 7x − 3 = 123

The solution of 7x − 3 = 123 is x = 18.

7x - 3 = 123\ \Rightarrow\ x = 18

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The lines y = 7x − 3 and y = 123 meet at x = 18. 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.
$7x - 3 = 123$
2
Add 3 to both sides:
$7x - 3 + 3 = 123 + 3 \ \Rightarrow\ 7x = 126$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{126}{7} \ \Rightarrow\ x = 18$
4
Check: put x = 18 back into the equation.
$7\cdot18 - 3 = 126 - 3 = 123 \checkmark$

LaTeX source of the formulas on this page

\[ 7x - 3 = 123\ \Rightarrow\ x = 18 \]
\[ 7x - 3 = 123 \]
\[ 7x - 3 + 3 = 123 + 3 \ \Rightarrow\ 7x = 126 \]
\[ \frac{7x}{7} = \frac{126}{7} \ \Rightarrow\ x = 18 \]
\[ 7\cdot18 - 3 = 126 - 3 = 123 \checkmark \]

Trying values of x in 7x − 3 = 123

x	7x − 3	Equals 123?
16	109	no
17	116	no
18	123	yes
19	130	no
20	137	no

Questions

What is x in 7x − 3 = 123?

The solution of 7x − 3 = 123 is x = 18.

How do you solve 7x − 3 = 123?

Add 3 to both sides to get 7x = 126, then divide both sides by 7 to get x = 18.

How do I check the answer?

Replace x by 18: 7(18) − 3 = 123, which is 123.

Solve 7x − 3 = 123

How to work it out

Trying values of x in 7x − 3 = 123

Questions

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