Solve 7x − 9 = −30

The solution of 7x − 9 = −30 is x = -3.

7x - 9 = -30\ \Rightarrow\ x = -3

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The lines y = 7x − 9 and y = -30 meet at x = -3. 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.
$7x - 9 = -30$
2
Add 9 to both sides:
$7x - 9 + 9 = -30 + 9 \ \Rightarrow\ 7x = -21$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{-21}{7} \ \Rightarrow\ x = -3$
4
Check: put x = -3 back into the equation.
$7\cdot(-3) - 9 = -21 - 9 = -30 \checkmark$

LaTeX source of the formulas on this page

\[ 7x - 9 = -30\ \Rightarrow\ x = -3 \]
\[ 7x - 9 = -30 \]
\[ 7x - 9 + 9 = -30 + 9 \ \Rightarrow\ 7x = -21 \]
\[ \frac{7x}{7} = \frac{-21}{7} \ \Rightarrow\ x = -3 \]
\[ 7\cdot(-3) - 9 = -21 - 9 = -30 \checkmark \]

Trying values of x in 7x − 9 = −30

x	7x − 9	Equals -30?
-5	-44	no
-4	-37	no
-3	-30	yes
-2	-23	no
-1	-16	no

Questions

What is x in 7x − 9 = −30?

The solution of 7x − 9 = −30 is x = -3.

How do you solve 7x − 9 = −30?

Add 9 to both sides to get 7x = -21, then divide both sides by 7 to get x = -3.

How do I check the answer?

Replace x by -3: 7(-3) − 9 = -30, which is -30.

Solve 7x − 9 = −30

How to work it out

Trying values of x in 7x − 9 = −30

Questions

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