Solve 8x − 4 = 84

The solution of 8x − 4 = 84 is x = 11.

8x - 4 = 84\ \Rightarrow\ x = 11

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The lines y = 8x − 4 and y = 84 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.
$8x - 4 = 84$
2
Add 4 to both sides:
$8x - 4 + 4 = 84 + 4 \ \Rightarrow\ 8x = 88$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{88}{8} \ \Rightarrow\ x = 11$
4
Check: put x = 11 back into the equation.
$8\cdot11 - 4 = 88 - 4 = 84 \checkmark$

LaTeX source of the formulas on this page

\[ 8x - 4 = 84\ \Rightarrow\ x = 11 \]
\[ 8x - 4 = 84 \]
\[ 8x - 4 + 4 = 84 + 4 \ \Rightarrow\ 8x = 88 \]
\[ \frac{8x}{8} = \frac{88}{8} \ \Rightarrow\ x = 11 \]
\[ 8\cdot11 - 4 = 88 - 4 = 84 \checkmark \]

Trying values of x in 8x − 4 = 84

x	8x − 4	Equals 84?
9	68	no
10	76	no
11	84	yes
12	92	no
13	100	no

Questions

What is x in 8x − 4 = 84?

The solution of 8x − 4 = 84 is x = 11.

How do you solve 8x − 4 = 84?

Add 4 to both sides to get 8x = 88, then divide both sides by 8 to get x = 11.

How do I check the answer?

Replace x by 11: 8(11) − 4 = 84, which is 84.

Solve 8x − 4 = 84

How to work it out

Trying values of x in 8x − 4 = 84

Questions

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