Solve 10x − 1 = 139

The solution of 10x − 1 = 139 is x = 14.

10x - 1 = 139\ \Rightarrow\ x = 14

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The lines y = 10x − 1 and y = 139 meet at x = 14. 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.
$10x - 1 = 139$
2
Add 1 to both sides:
$10x - 1 + 1 = 139 + 1 \ \Rightarrow\ 10x = 140$
3
Divide both sides by 10:
$\frac{10x}{10} = \frac{140}{10} \ \Rightarrow\ x = 14$
4
Check: put x = 14 back into the equation.
$10\cdot14 - 1 = 140 - 1 = 139 \checkmark$

LaTeX source of the formulas on this page

\[ 10x - 1 = 139\ \Rightarrow\ x = 14 \]
\[ 10x - 1 = 139 \]
\[ 10x - 1 + 1 = 139 + 1 \ \Rightarrow\ 10x = 140 \]
\[ \frac{10x}{10} = \frac{140}{10} \ \Rightarrow\ x = 14 \]
\[ 10\cdot14 - 1 = 140 - 1 = 139 \checkmark \]

Trying values of x in 10x − 1 = 139

x	10x − 1	Equals 139?
12	119	no
13	129	no
14	139	yes
15	149	no
16	159	no

Questions

What is x in 10x − 1 = 139?

The solution of 10x − 1 = 139 is x = 14.

How do you solve 10x − 1 = 139?

Add 1 to both sides to get 10x = 140, then divide both sides by 10 to get x = 14.

How do I check the answer?

Replace x by 14: 10(14) − 1 = 139, which is 139.

Solve 10x − 1 = 139

How to work it out

Trying values of x in 10x − 1 = 139

Questions

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