Solve 7x − 4 = 80

The solution of 7x − 4 = 80 is x = 12.

7x - 4 = 80\ \Rightarrow\ x = 12

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The lines y = 7x − 4 and y = 80 meet at x = 12. 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.
$7x - 4 = 80$
2
Add 4 to both sides:
$7x - 4 + 4 = 80 + 4 \ \Rightarrow\ 7x = 84$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{84}{7} \ \Rightarrow\ x = 12$
4
Check: put x = 12 back into the equation.
$7\cdot12 - 4 = 84 - 4 = 80 \checkmark$

LaTeX source of the formulas on this page

\[ 7x - 4 = 80\ \Rightarrow\ x = 12 \]
\[ 7x - 4 = 80 \]
\[ 7x - 4 + 4 = 80 + 4 \ \Rightarrow\ 7x = 84 \]
\[ \frac{7x}{7} = \frac{84}{7} \ \Rightarrow\ x = 12 \]
\[ 7\cdot12 - 4 = 84 - 4 = 80 \checkmark \]

Trying values of x in 7x − 4 = 80

x	7x − 4	Equals 80?
10	66	no
11	73	no
12	80	yes
13	87	no
14	94	no

Questions

What is x in 7x − 4 = 80?

The solution of 7x − 4 = 80 is x = 12.

How do you solve 7x − 4 = 80?

Add 4 to both sides to get 7x = 84, then divide both sides by 7 to get x = 12.

How do I check the answer?

Replace x by 12: 7(12) − 4 = 80, which is 80.

Solve 7x − 4 = 80

How to work it out

Trying values of x in 7x − 4 = 80

Questions

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