Solve 5x + 15 = −20

The solution of 5x + 15 = −20 is x = -7.

5x + 15 = -20\ \Rightarrow\ x = -7

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The lines y = 5x + 15 and y = -20 meet at x = -7. 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 addition, then the multiplication.
$5x + 15 = -20$
2
Subtract 15 from both sides:
$5x + 15 - 15 = -20 - 15 \ \Rightarrow\ 5x = -35$
3
Divide both sides by 5:
$\frac{5x}{5} = \frac{-35}{5} \ \Rightarrow\ x = -7$
4
Check: put x = -7 back into the equation.
$5\cdot(-7) + 15 = -35 + 15 = -20 \checkmark$

LaTeX source of the formulas on this page

\[ 5x + 15 = -20\ \Rightarrow\ x = -7 \]
\[ 5x + 15 = -20 \]
\[ 5x + 15 - 15 = -20 - 15 \ \Rightarrow\ 5x = -35 \]
\[ \frac{5x}{5} = \frac{-35}{5} \ \Rightarrow\ x = -7 \]
\[ 5\cdot(-7) + 15 = -35 + 15 = -20 \checkmark \]

Trying values of x in 5x + 15 = −20

x	5x + 15	Equals -20?
-9	-30	no
-8	-25	no
-7	-20	yes
-6	-15	no
-5	-10	no

Questions

What is x in 5x + 15 = −20?

The solution of 5x + 15 = −20 is x = -7.

How do you solve 5x + 15 = −20?

Subtract 15 from both sides to get 5x = -35, then divide both sides by 5 to get x = -7.

How do I check the answer?

Replace x by -7: 5(-7) + 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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