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 addition, then the multiplication.
$5x + 15 = -25$
2
Subtract 15 from 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.
$5\cdot(-8) + 15 = -40 + 15 = -25 \checkmark$

LaTeX source of the formulas on this page

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

Trying values of x in 5x + 15 = −25

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

Subtract 15 from 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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