Solve 5x − 15 = −20

The solution of 5x − 15 = −20 is x = -1.

5x - 15 = -20\ \Rightarrow\ x = -1

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The lines y = 5x − 15 and y = -20 meet at x = -1. 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.
$5x - 15 = -20$
2
Add 15 to both sides:
$5x - 15 + 15 = -20 + 15 \ \Rightarrow\ 5x = -5$
3
Divide both sides by 5:
$\frac{5x}{5} = \frac{-5}{5} \ \Rightarrow\ x = -1$
4
Check: put x = -1 back into the equation.
$5\cdot(-1) - 15 = -5 - 15 = -20 \checkmark$

LaTeX source of the formulas on this page

\[ 5x - 15 = -20\ \Rightarrow\ x = -1 \]
\[ 5x - 15 = -20 \]
\[ 5x - 15 + 15 = -20 + 15 \ \Rightarrow\ 5x = -5 \]
\[ \frac{5x}{5} = \frac{-5}{5} \ \Rightarrow\ x = -1 \]
\[ 5\cdot(-1) - 15 = -5 - 15 = -20 \checkmark \]

Trying values of x in 5x − 15 = −20

x	5x − 15	Equals -20?
-3	-30	no
-2	-25	no
-1	-20	yes
0	-15	no
1	-10	no

Questions

What is x in 5x − 15 = −20?

The solution of 5x − 15 = −20 is x = -1.

How do you solve 5x − 15 = −20?

Add 15 to both sides to get 5x = -5, then divide both sides by 5 to get x = -1.

How do I check the answer?

Replace x by -1: 5(-1) − 15 = -20, which is -20.

Solve 5x − 15 = −20

How to work it out

Trying values of x in 5x − 15 = −20

Questions

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