Solve 5x − 15 = 25

The solution of 5x − 15 = 25 is x = 8.

5x - 15 = 25\ \Rightarrow\ x = 8

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The lines y = 5x − 15 and y = 25 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 subtraction, then the multiplication.
$5x - 15 = 25$
2
Add 15 to both sides:
$5x - 15 + 15 = 25 + 15 \ \Rightarrow\ 5x = 40$
3
Divide both sides by 5:
$\frac{5x}{5} = \frac{40}{5} \ \Rightarrow\ x = 8$
4
Check: put x = 8 back into the equation.
$5\cdot8 - 15 = 40 - 15 = 25 \checkmark$

LaTeX source of the formulas on this page

\[ 5x - 15 = 25\ \Rightarrow\ x = 8 \]
\[ 5x - 15 = 25 \]
\[ 5x - 15 + 15 = 25 + 15 \ \Rightarrow\ 5x = 40 \]
\[ \frac{5x}{5} = \frac{40}{5} \ \Rightarrow\ x = 8 \]
\[ 5\cdot8 - 15 = 40 - 15 = 25 \checkmark \]

Trying values of x in 5x − 15 = 25

x	5x − 15	Equals 25?
6	15	no
7	20	no
8	25	yes
9	30	no
10	35	no

Questions

What is x in 5x − 15 = 25?

The solution of 5x − 15 = 25 is x = 8.

How do you solve 5x − 15 = 25?

Add 15 to both sides to get 5x = 40, then divide both sides by 5 to get x = 8.

How do I check the answer?

Replace x by 8: 5(8) − 15 = 25, which is 25.

Solve 5x − 15 = 25

How to work it out

Trying values of x in 5x − 15 = 25

Questions

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