Solve 8x − 4 = 100

The solution of 8x − 4 = 100 is x = 13.

8x - 4 = 100\ \Rightarrow\ x = 13

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The lines y = 8x − 4 and y = 100 meet at x = 13. 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.
$8x - 4 = 100$
2
Add 4 to both sides:
$8x - 4 + 4 = 100 + 4 \ \Rightarrow\ 8x = 104$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{104}{8} \ \Rightarrow\ x = 13$
4
Check: put x = 13 back into the equation.
$8\cdot13 - 4 = 104 - 4 = 100 \checkmark$

LaTeX source of the formulas on this page

\[ 8x - 4 = 100\ \Rightarrow\ x = 13 \]
\[ 8x - 4 = 100 \]
\[ 8x - 4 + 4 = 100 + 4 \ \Rightarrow\ 8x = 104 \]
\[ \frac{8x}{8} = \frac{104}{8} \ \Rightarrow\ x = 13 \]
\[ 8\cdot13 - 4 = 104 - 4 = 100 \checkmark \]

Trying values of x in 8x − 4 = 100

x	8x − 4	Equals 100?
11	84	no
12	92	no
13	100	yes
14	108	no
15	116	no

Questions

What is x in 8x − 4 = 100?

The solution of 8x − 4 = 100 is x = 13.

How do you solve 8x − 4 = 100?

Add 4 to both sides to get 8x = 104, then divide both sides by 8 to get x = 13.

How do I check the answer?

Replace x by 13: 8(13) − 4 = 100, which is 100.

Solve 8x − 4 = 100

How to work it out

Trying values of x in 8x − 4 = 100

Questions

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