Solve 8x + 13 = 77

The solution of 8x + 13 = 77 is x = 8.

8x + 13 = 77\ \Rightarrow\ x = 8

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The lines y = 8x + 13 and y = 77 meet at x = 8. 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 addition, then the multiplication.
$8x + 13 = 77$
2
Subtract 13 from both sides:
$8x + 13 - 13 = 77 - 13 \ \Rightarrow\ 8x = 64$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{64}{8} \ \Rightarrow\ x = 8$
4
Check: put x = 8 back into the equation.
$8\cdot8 + 13 = 64 + 13 = 77 \checkmark$

LaTeX source of the formulas on this page

\[ 8x + 13 = 77\ \Rightarrow\ x = 8 \]
\[ 8x + 13 = 77 \]
\[ 8x + 13 - 13 = 77 - 13 \ \Rightarrow\ 8x = 64 \]
\[ \frac{8x}{8} = \frac{64}{8} \ \Rightarrow\ x = 8 \]
\[ 8\cdot8 + 13 = 64 + 13 = 77 \checkmark \]

Trying values of x in 8x + 13 = 77

x	8x + 13	Equals 77?
6	61	no
7	69	no
8	77	yes
9	85	no
10	93	no

Questions

What is x in 8x + 13 = 77?

The solution of 8x + 13 = 77 is x = 8.

How do you solve 8x + 13 = 77?

Subtract 13 from both sides to get 8x = 64, then divide both sides by 8 to get x = 8.

How do I check the answer?

Replace x by 8: 8(8) + 13 = 77, which is 77.

Solve 8x + 13 = 77

How to work it out

Trying values of x in 8x + 13 = 77

Questions

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