Solve 12x − 4 = 128

The solution of 12x − 4 = 128 is x = 11.

12x - 4 = 128\ \Rightarrow\ x = 11

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The lines y = 12x − 4 and y = 128 meet at x = 11. 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.
$12x - 4 = 128$
2
Add 4 to both sides:
$12x - 4 + 4 = 128 + 4 \ \Rightarrow\ 12x = 132$
3
Divide both sides by 12:
$\frac{12x}{12} = \frac{132}{12} \ \Rightarrow\ x = 11$
4
Check: put x = 11 back into the equation.
$12\cdot11 - 4 = 132 - 4 = 128 \checkmark$

LaTeX source of the formulas on this page

\[ 12x - 4 = 128\ \Rightarrow\ x = 11 \]
\[ 12x - 4 = 128 \]
\[ 12x - 4 + 4 = 128 + 4 \ \Rightarrow\ 12x = 132 \]
\[ \frac{12x}{12} = \frac{132}{12} \ \Rightarrow\ x = 11 \]
\[ 12\cdot11 - 4 = 132 - 4 = 128 \checkmark \]

Trying values of x in 12x − 4 = 128

x	12x − 4	Equals 128?
9	104	no
10	116	no
11	128	yes
12	140	no
13	152	no

Questions

What is x in 12x − 4 = 128?

The solution of 12x − 4 = 128 is x = 11.

How do you solve 12x − 4 = 128?

Add 4 to both sides to get 12x = 132, then divide both sides by 12 to get x = 11.

How do I check the answer?

Replace x by 11: 12(11) − 4 = 128, which is 128.

Solve 12x − 4 = 128

How to work it out

Trying values of x in 12x − 4 = 128

Questions

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