Solve 7x − 11 = 129

The solution of 7x − 11 = 129 is x = 20.

7x - 11 = 129\ \Rightarrow\ x = 20

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The lines y = 7x − 11 and y = 129 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.
$7x - 11 = 129$
2
Add 11 to both sides:
$7x - 11 + 11 = 129 + 11 \ \Rightarrow\ 7x = 140$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{140}{7} \ \Rightarrow\ x = 20$
4
Check: put x = 20 back into the equation.
$7\cdot20 - 11 = 140 - 11 = 129 \checkmark$

LaTeX source of the formulas on this page

\[ 7x - 11 = 129\ \Rightarrow\ x = 20 \]
\[ 7x - 11 = 129 \]
\[ 7x - 11 + 11 = 129 + 11 \ \Rightarrow\ 7x = 140 \]
\[ \frac{7x}{7} = \frac{140}{7} \ \Rightarrow\ x = 20 \]
\[ 7\cdot20 - 11 = 140 - 11 = 129 \checkmark \]

Trying values of x in 7x − 11 = 129

x	7x − 11	Equals 129?
18	115	no
19	122	no
20	129	yes
21	136	no
22	143	no

Questions

What is x in 7x − 11 = 129?

The solution of 7x − 11 = 129 is x = 20.

How do you solve 7x − 11 = 129?

Add 11 to both sides to get 7x = 140, then divide both sides by 7 to get x = 20.

How do I check the answer?

Replace x by 20: 7(20) − 11 = 129, which is 129.

Solve 7x − 11 = 129

How to work it out

Trying values of x in 7x − 11 = 129

Questions

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