Solve 5x − 2 = 78

The solution of 5x − 2 = 78 is x = 16.

5x - 2 = 78\ \Rightarrow\ x = 16

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The lines y = 5x − 2 and y = 78 meet at x = 16. 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.
$5x - 2 = 78$
2
Add 2 to both sides:
$5x - 2 + 2 = 78 + 2 \ \Rightarrow\ 5x = 80$
3
Divide both sides by 5:
$\frac{5x}{5} = \frac{80}{5} \ \Rightarrow\ x = 16$
4
Check: put x = 16 back into the equation.
$5\cdot16 - 2 = 80 - 2 = 78 \checkmark$

LaTeX source of the formulas on this page

\[ 5x - 2 = 78\ \Rightarrow\ x = 16 \]
\[ 5x - 2 = 78 \]
\[ 5x - 2 + 2 = 78 + 2 \ \Rightarrow\ 5x = 80 \]
\[ \frac{5x}{5} = \frac{80}{5} \ \Rightarrow\ x = 16 \]
\[ 5\cdot16 - 2 = 80 - 2 = 78 \checkmark \]

Trying values of x in 5x − 2 = 78

x	5x − 2	Equals 78?
14	68	no
15	73	no
16	78	yes
17	83	no
18	88	no

Questions

What is x in 5x − 2 = 78?

The solution of 5x − 2 = 78 is x = 16.

How do you solve 5x − 2 = 78?

Add 2 to both sides to get 5x = 80, then divide both sides by 5 to get x = 16.

How do I check the answer?

Replace x by 16: 5(16) − 2 = 78, which is 78.

Solve 5x − 2 = 78

How to work it out

Trying values of x in 5x − 2 = 78

Questions

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