Solve 5x − 15 = −40

The solution of 5x − 15 = −40 is x = -5.

5x - 15 = -40\ \Rightarrow\ x = -5

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The lines y = 5x − 15 and y = -40 meet at x = -5. 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.
$5x - 15 = -40$
2
Add 15 to both sides:
$5x - 15 + 15 = -40 + 15 \ \Rightarrow\ 5x = -25$
3
Divide both sides by 5:
$\frac{5x}{5} = \frac{-25}{5} \ \Rightarrow\ x = -5$
4
Check: put x = -5 back into the equation.
$5\cdot(-5) - 15 = -25 - 15 = -40 \checkmark$

LaTeX source of the formulas on this page

\[ 5x - 15 = -40\ \Rightarrow\ x = -5 \]
\[ 5x - 15 = -40 \]
\[ 5x - 15 + 15 = -40 + 15 \ \Rightarrow\ 5x = -25 \]
\[ \frac{5x}{5} = \frac{-25}{5} \ \Rightarrow\ x = -5 \]
\[ 5\cdot(-5) - 15 = -25 - 15 = -40 \checkmark \]

Trying values of x in 5x − 15 = −40

x	5x − 15	Equals -40?
-7	-50	no
-6	-45	no
-5	-40	yes
-4	-35	no
-3	-30	no

Questions

What is x in 5x − 15 = −40?

The solution of 5x − 15 = −40 is x = -5.

How do you solve 5x − 15 = −40?

Add 15 to both sides to get 5x = -25, then divide both sides by 5 to get x = -5.

How do I check the answer?

Replace x by -5: 5(-5) − 15 = -40, which is -40.

Solve 5x − 15 = −40

How to work it out

Trying values of x in 5x − 15 = −40

Questions

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