Solve 4x − 8 = 28

The solution of 4x − 8 = 28 is x = 9.

4x - 8 = 28\ \Rightarrow\ x = 9

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The lines y = 4x − 8 and y = 28 meet at x = 9. 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.
$4x - 8 = 28$
2
Add 8 to both sides:
$4x - 8 + 8 = 28 + 8 \ \Rightarrow\ 4x = 36$
3
Divide both sides by 4:
$\frac{4x}{4} = \frac{36}{4} \ \Rightarrow\ x = 9$
4
Check: put x = 9 back into the equation.
$4\cdot9 - 8 = 36 - 8 = 28 \checkmark$

LaTeX source of the formulas on this page

\[ 4x - 8 = 28\ \Rightarrow\ x = 9 \]
\[ 4x - 8 = 28 \]
\[ 4x - 8 + 8 = 28 + 8 \ \Rightarrow\ 4x = 36 \]
\[ \frac{4x}{4} = \frac{36}{4} \ \Rightarrow\ x = 9 \]
\[ 4\cdot9 - 8 = 36 - 8 = 28 \checkmark \]

Trying values of x in 4x − 8 = 28

x	4x − 8	Equals 28?
7	20	no
8	24	no
9	28	yes
10	32	no
11	36	no

Questions

What is x in 4x − 8 = 28?

The solution of 4x − 8 = 28 is x = 9.

How do you solve 4x − 8 = 28?

Add 8 to both sides to get 4x = 36, then divide both sides by 4 to get x = 9.

How do I check the answer?

Replace x by 9: 4(9) − 8 = 28, which is 28.

Solve 4x − 8 = 28

How to work it out

Trying values of x in 4x − 8 = 28

Questions

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