Solve 7x − 12 = −40

The solution of 7x − 12 = −40 is x = -4.

7x - 12 = -40\ \Rightarrow\ x = -4

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The lines y = 7x − 12 and y = -40 meet at x = -4. 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.
$7x - 12 = -40$
2
Add 12 to both sides:
$7x - 12 + 12 = -40 + 12 \ \Rightarrow\ 7x = -28$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{-28}{7} \ \Rightarrow\ x = -4$
4
Check: put x = -4 back into the equation.
$7\cdot(-4) - 12 = -28 - 12 = -40 \checkmark$

LaTeX source of the formulas on this page

\[ 7x - 12 = -40\ \Rightarrow\ x = -4 \]
\[ 7x - 12 = -40 \]
\[ 7x - 12 + 12 = -40 + 12 \ \Rightarrow\ 7x = -28 \]
\[ \frac{7x}{7} = \frac{-28}{7} \ \Rightarrow\ x = -4 \]
\[ 7\cdot(-4) - 12 = -28 - 12 = -40 \checkmark \]

Trying values of x in 7x − 12 = −40

x	7x − 12	Equals -40?
-6	-54	no
-5	-47	no
-4	-40	yes
-3	-33	no
-2	-26	no

Questions

What is x in 7x − 12 = −40?

The solution of 7x − 12 = −40 is x = -4.

How do you solve 7x − 12 = −40?

Add 12 to both sides to get 7x = -28, then divide both sides by 7 to get x = -4.

How do I check the answer?

Replace x by -4: 7(-4) − 12 = -40, which is -40.

Solve 7x − 12 = −40

How to work it out

Trying values of x in 7x − 12 = −40

Questions

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