Solve 3x − 7 = 20

The solution of 3x − 7 = 20 is x = 9.

3x - 7 = 20\ \Rightarrow\ x = 9

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The lines y = 3x − 7 and y = 20 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 subtraction, then the multiplication.
$3x - 7 = 20$
2
Add 7 to both sides:
$3x - 7 + 7 = 20 + 7 \ \Rightarrow\ 3x = 27$
3
Divide both sides by 3:
$\frac{3x}{3} = \frac{27}{3} \ \Rightarrow\ x = 9$
4
Check: put x = 9 back into the equation.
$3\cdot9 - 7 = 27 - 7 = 20 \checkmark$

LaTeX source of the formulas on this page

\[ 3x - 7 = 20\ \Rightarrow\ x = 9 \]
\[ 3x - 7 = 20 \]
\[ 3x - 7 + 7 = 20 + 7 \ \Rightarrow\ 3x = 27 \]
\[ \frac{3x}{3} = \frac{27}{3} \ \Rightarrow\ x = 9 \]
\[ 3\cdot9 - 7 = 27 - 7 = 20 \checkmark \]

Trying values of x in 3x − 7 = 20

x	3x − 7	Equals 20?
7	14	no
8	17	no
9	20	yes
10	23	no
11	26	no

Questions

What is x in 3x − 7 = 20?

The solution of 3x − 7 = 20 is x = 9.

How do you solve 3x − 7 = 20?

Add 7 to both sides to get 3x = 27, then divide both sides by 3 to get x = 9.

How do I check the answer?

Replace x by 9: 3(9) − 7 = 20, which is 20.

Solve 3x − 7 = 20

How to work it out

Trying values of x in 3x − 7 = 20

Questions

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