Solve 3x + 7 = −8

The solution of 3x + 7 = −8 is x = -5.

3x + 7 = -8\ \Rightarrow\ x = -5

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The lines y = 3x + 7 and y = -8 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 addition, then the multiplication.
$3x + 7 = -8$
2
Subtract 7 from both sides:
$3x + 7 - 7 = -8 - 7 \ \Rightarrow\ 3x = -15$
3
Divide both sides by 3:
$\frac{3x}{3} = \frac{-15}{3} \ \Rightarrow\ x = -5$
4
Check: put x = -5 back into the equation.
$3\cdot(-5) + 7 = -15 + 7 = -8 \checkmark$

LaTeX source of the formulas on this page

\[ 3x + 7 = -8\ \Rightarrow\ x = -5 \]
\[ 3x + 7 = -8 \]
\[ 3x + 7 - 7 = -8 - 7 \ \Rightarrow\ 3x = -15 \]
\[ \frac{3x}{3} = \frac{-15}{3} \ \Rightarrow\ x = -5 \]
\[ 3\cdot(-5) + 7 = -15 + 7 = -8 \checkmark \]

Trying values of x in 3x + 7 = −8

x	3x + 7	Equals -8?
-7	-14	no
-6	-11	no
-5	-8	yes
-4	-5	no
-3	-2	no

Questions

What is x in 3x + 7 = −8?

The solution of 3x + 7 = −8 is x = -5.

How do you solve 3x + 7 = −8?

Subtract 7 from both sides to get 3x = -15, then divide both sides by 3 to get x = -5.

How do I check the answer?

Replace x by -5: 3(-5) + 7 = -8, which is -8.

Solve 3x + 7 = −8

How to work it out

Trying values of x in 3x + 7 = −8

Questions

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