Solve 8x − 11 = 21

The solution of 8x − 11 = 21 is x = 4.

8x - 11 = 21\ \Rightarrow\ x = 4

Explain it step by step in chat Make a short video of it

The lines y = 8x − 11 and y = 21 meet at x = 4. 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.
$8x - 11 = 21$
2
Add 11 to both sides:
$8x - 11 + 11 = 21 + 11 \ \Rightarrow\ 8x = 32$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{32}{8} \ \Rightarrow\ x = 4$
4
Check: put x = 4 back into the equation.
$8\cdot4 - 11 = 32 - 11 = 21 \checkmark$

LaTeX source of the formulas on this page

\[ 8x - 11 = 21\ \Rightarrow\ x = 4 \]
\[ 8x - 11 = 21 \]
\[ 8x - 11 + 11 = 21 + 11 \ \Rightarrow\ 8x = 32 \]
\[ \frac{8x}{8} = \frac{32}{8} \ \Rightarrow\ x = 4 \]
\[ 8\cdot4 - 11 = 32 - 11 = 21 \checkmark \]

Trying values of x in 8x − 11 = 21

x	8x − 11	Equals 21?
2	5	no
3	13	no
4	21	yes
5	29	no
6	37	no

Questions

What is x in 8x − 11 = 21?

The solution of 8x − 11 = 21 is x = 4.

How do you solve 8x − 11 = 21?

Add 11 to both sides to get 8x = 32, then divide both sides by 8 to get x = 4.

How do I check the answer?

Replace x by 4: 8(4) − 11 = 21, which is 21.

Solve 8x − 11 = 21

How to work it out

Trying values of x in 8x − 11 = 21

Questions

Similar equations