Solve 5x − 15 = 55

The solution of 5x − 15 = 55 is x = 14.

5x - 15 = 55\ \Rightarrow\ x = 14

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The lines y = 5x − 15 and y = 55 meet at x = 14. 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.
$5x - 15 = 55$
2
Add 15 to both sides:
$5x - 15 + 15 = 55 + 15 \ \Rightarrow\ 5x = 70$
3
Divide both sides by 5:
$\frac{5x}{5} = \frac{70}{5} \ \Rightarrow\ x = 14$
4
Check: put x = 14 back into the equation.
$5\cdot14 - 15 = 70 - 15 = 55 \checkmark$

LaTeX source of the formulas on this page

\[ 5x - 15 = 55\ \Rightarrow\ x = 14 \]
\[ 5x - 15 = 55 \]
\[ 5x - 15 + 15 = 55 + 15 \ \Rightarrow\ 5x = 70 \]
\[ \frac{5x}{5} = \frac{70}{5} \ \Rightarrow\ x = 14 \]
\[ 5\cdot14 - 15 = 70 - 15 = 55 \checkmark \]

Trying values of x in 5x − 15 = 55

x	5x − 15	Equals 55?
12	45	no
13	50	no
14	55	yes
15	60	no
16	65	no

Questions

What is x in 5x − 15 = 55?

The solution of 5x − 15 = 55 is x = 14.

How do you solve 5x − 15 = 55?

Add 15 to both sides to get 5x = 70, then divide both sides by 5 to get x = 14.

How do I check the answer?

Replace x by 14: 5(14) − 15 = 55, which is 55.

Solve 5x − 15 = 55

How to work it out

Trying values of x in 5x − 15 = 55

Questions

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