Solve 8x − 7 = 121

The solution of 8x − 7 = 121 is x = 16.

8x - 7 = 121\ \Rightarrow\ x = 16

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The lines y = 8x − 7 and y = 121 meet at x = 16. 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.
$8x - 7 = 121$
2
Add 7 to both sides:
$8x - 7 + 7 = 121 + 7 \ \Rightarrow\ 8x = 128$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{128}{8} \ \Rightarrow\ x = 16$
4
Check: put x = 16 back into the equation.
$8\cdot16 - 7 = 128 - 7 = 121 \checkmark$

LaTeX source of the formulas on this page

\[ 8x - 7 = 121\ \Rightarrow\ x = 16 \]
\[ 8x - 7 = 121 \]
\[ 8x - 7 + 7 = 121 + 7 \ \Rightarrow\ 8x = 128 \]
\[ \frac{8x}{8} = \frac{128}{8} \ \Rightarrow\ x = 16 \]
\[ 8\cdot16 - 7 = 128 - 7 = 121 \checkmark \]

Trying values of x in 8x − 7 = 121

x	8x − 7	Equals 121?
14	105	no
15	113	no
16	121	yes
17	129	no
18	137	no

Questions

What is x in 8x − 7 = 121?

The solution of 8x − 7 = 121 is x = 16.

How do you solve 8x − 7 = 121?

Add 7 to both sides to get 8x = 128, then divide both sides by 8 to get x = 16.

How do I check the answer?

Replace x by 16: 8(16) − 7 = 121, which is 121.

Solve 8x − 7 = 121

How to work it out

Trying values of x in 8x − 7 = 121

Questions

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