Solve 4x − 2 = 78

The solution of 4x − 2 = 78 is x = 20.

4x - 2 = 78\ \Rightarrow\ x = 20

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The lines y = 4x − 2 and y = 78 meet at x = 20. 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.
$4x - 2 = 78$
2
Add 2 to both sides:
$4x - 2 + 2 = 78 + 2 \ \Rightarrow\ 4x = 80$
3
Divide both sides by 4:
$\frac{4x}{4} = \frac{80}{4} \ \Rightarrow\ x = 20$
4
Check: put x = 20 back into the equation.
$4\cdot20 - 2 = 80 - 2 = 78 \checkmark$

LaTeX source of the formulas on this page

\[ 4x - 2 = 78\ \Rightarrow\ x = 20 \]
\[ 4x - 2 = 78 \]
\[ 4x - 2 + 2 = 78 + 2 \ \Rightarrow\ 4x = 80 \]
\[ \frac{4x}{4} = \frac{80}{4} \ \Rightarrow\ x = 20 \]
\[ 4\cdot20 - 2 = 80 - 2 = 78 \checkmark \]

Trying values of x in 4x − 2 = 78

x	4x − 2	Equals 78?
18	70	no
19	74	no
20	78	yes
21	82	no
22	86	no

Questions

What is x in 4x − 2 = 78?

The solution of 4x − 2 = 78 is x = 20.

How do you solve 4x − 2 = 78?

Add 2 to both sides to get 4x = 80, then divide both sides by 4 to get x = 20.

How do I check the answer?

Replace x by 20: 4(20) − 2 = 78, which is 78.

Solve 4x − 2 = 78

How to work it out

Trying values of x in 4x − 2 = 78

Questions

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