Solve 7x − 1 = 139

The solution of 7x − 1 = 139 is x = 20.

7x - 1 = 139\ \Rightarrow\ x = 20

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The lines y = 7x − 1 and y = 139 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.
$7x - 1 = 139$
2
Add 1 to both sides:
$7x - 1 + 1 = 139 + 1 \ \Rightarrow\ 7x = 140$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{140}{7} \ \Rightarrow\ x = 20$
4
Check: put x = 20 back into the equation.
$7\cdot20 - 1 = 140 - 1 = 139 \checkmark$

LaTeX source of the formulas on this page

\[ 7x - 1 = 139\ \Rightarrow\ x = 20 \]
\[ 7x - 1 = 139 \]
\[ 7x - 1 + 1 = 139 + 1 \ \Rightarrow\ 7x = 140 \]
\[ \frac{7x}{7} = \frac{140}{7} \ \Rightarrow\ x = 20 \]
\[ 7\cdot20 - 1 = 140 - 1 = 139 \checkmark \]

Trying values of x in 7x − 1 = 139

x	7x − 1	Equals 139?
18	125	no
19	132	no
20	139	yes
21	146	no
22	153	no

Questions

What is x in 7x − 1 = 139?

The solution of 7x − 1 = 139 is x = 20.

How do you solve 7x − 1 = 139?

Add 1 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) − 1 = 139, which is 139.

Solve 7x − 1 = 139

How to work it out

Trying values of x in 7x − 1 = 139

Questions

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