Solve 5x − 15 = −55

The solution of 5x − 15 = −55 is x = -8.

5x - 15 = -55\ \Rightarrow\ x = -8

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The lines y = 5x − 15 and y = -55 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.
$5x - 15 = -55$
2
Add 15 to both sides:
$5x - 15 + 15 = -55 + 15 \ \Rightarrow\ 5x = -40$
3
Divide both sides by 5:
$\frac{5x}{5} = \frac{-40}{5} \ \Rightarrow\ x = -8$
4
Check: put x = -8 back into the equation.
$5\cdot(-8) - 15 = -40 - 15 = -55 \checkmark$

LaTeX source of the formulas on this page

\[ 5x - 15 = -55\ \Rightarrow\ x = -8 \]
\[ 5x - 15 = -55 \]
\[ 5x - 15 + 15 = -55 + 15 \ \Rightarrow\ 5x = -40 \]
\[ \frac{5x}{5} = \frac{-40}{5} \ \Rightarrow\ x = -8 \]
\[ 5\cdot(-8) - 15 = -40 - 15 = -55 \checkmark \]

Trying values of x in 5x − 15 = −55

x	5x − 15	Equals -55?
-10	-65	no
-9	-60	no
-8	-55	yes
-7	-50	no
-6	-45	no

Questions

What is x in 5x − 15 = −55?

The solution of 5x − 15 = −55 is x = -8.

How do you solve 5x − 15 = −55?

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 = -55, which is -55.

Solve 5x − 15 = −55

How to work it out

Trying values of x in 5x − 15 = −55

Questions

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