Solve 5x − 13 = 87

The solution of 5x − 13 = 87 is x = 20.

5x - 13 = 87\ \Rightarrow\ x = 20

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The lines y = 5x − 13 and y = 87 meet at x = 20. 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.
$5x - 13 = 87$
2
Add 13 to both sides:
$5x - 13 + 13 = 87 + 13 \ \Rightarrow\ 5x = 100$
3
Divide both sides by 5:
$\frac{5x}{5} = \frac{100}{5} \ \Rightarrow\ x = 20$
4
Check: put x = 20 back into the equation.
$5\cdot20 - 13 = 100 - 13 = 87 \checkmark$

LaTeX source of the formulas on this page

\[ 5x - 13 = 87\ \Rightarrow\ x = 20 \]
\[ 5x - 13 = 87 \]
\[ 5x - 13 + 13 = 87 + 13 \ \Rightarrow\ 5x = 100 \]
\[ \frac{5x}{5} = \frac{100}{5} \ \Rightarrow\ x = 20 \]
\[ 5\cdot20 - 13 = 100 - 13 = 87 \checkmark \]

Trying values of x in 5x − 13 = 87

x	5x − 13	Equals 87?
18	77	no
19	82	no
20	87	yes
21	92	no
22	97	no

Questions

What is x in 5x − 13 = 87?

The solution of 5x − 13 = 87 is x = 20.

How do you solve 5x − 13 = 87?

Add 13 to both sides to get 5x = 100, then divide both sides by 5 to get x = 20.

How do I check the answer?

Replace x by 20: 5(20) − 13 = 87, which is 87.

Solve 5x − 13 = 87

How to work it out

Trying values of x in 5x − 13 = 87

Questions

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