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 subtraction, then the multiplication.
$3x - 7 = 8$
2
Add 7 to 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.
$3\cdot5 - 7 = 15 - 7 = 8 \checkmark$

LaTeX source of the formulas on this page

\[ 3x - 7 = 8\ \Rightarrow\ x = 5 \]
\[ 3x - 7 = 8 \]
\[ 3x - 7 + 7 = 8 + 7 \ \Rightarrow\ 3x = 15 \]
\[ \frac{3x}{3} = \frac{15}{3} \ \Rightarrow\ x = 5 \]
\[ 3\cdot5 - 7 = 15 - 7 = 8 \checkmark \]

Trying values of x in 3x − 7 = 8

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

Add 7 to 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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