Solve 10x + 12 = −78

The solution of 10x + 12 = −78 is x = -9.

10x + 12 = -78\ \Rightarrow\ x = -9

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The lines y = 10x + 12 and y = -78 meet at x = -9. 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.
$10x + 12 = -78$
2
Subtract 12 from both sides:
$10x + 12 - 12 = -78 - 12 \ \Rightarrow\ 10x = -90$
3
Divide both sides by 10:
$\frac{10x}{10} = \frac{-90}{10} \ \Rightarrow\ x = -9$
4
Check: put x = -9 back into the equation.
$10\cdot(-9) + 12 = -90 + 12 = -78 \checkmark$

LaTeX source of the formulas on this page

\[ 10x + 12 = -78\ \Rightarrow\ x = -9 \]
\[ 10x + 12 = -78 \]
\[ 10x + 12 - 12 = -78 - 12 \ \Rightarrow\ 10x = -90 \]
\[ \frac{10x}{10} = \frac{-90}{10} \ \Rightarrow\ x = -9 \]
\[ 10\cdot(-9) + 12 = -90 + 12 = -78 \checkmark \]

Trying values of x in 10x + 12 = −78

x	10x + 12	Equals -78?
-11	-98	no
-10	-88	no
-9	-78	yes
-8	-68	no
-7	-58	no

Questions

What is x in 10x + 12 = −78?

The solution of 10x + 12 = −78 is x = -9.

How do you solve 10x + 12 = −78?

Subtract 12 from both sides to get 10x = -90, then divide both sides by 10 to get x = -9.

How do I check the answer?

Replace x by -9: 10(-9) + 12 = -78, which is -78.

Solve 10x + 12 = −78

How to work it out

Trying values of x in 10x + 12 = −78

Questions

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