Solve 4x − 15 = 65

The solution of 4x − 15 = 65 is x = 20.

4x - 15 = 65\ \Rightarrow\ x = 20

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The lines y = 4x − 15 and y = 65 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.
$4x - 15 = 65$
2
Add 15 to both sides:
$4x - 15 + 15 = 65 + 15 \ \Rightarrow\ 4x = 80$
3
Divide both sides by 4:
$\frac{4x}{4} = \frac{80}{4} \ \Rightarrow\ x = 20$
4
Check: put x = 20 back into the equation.
$4\cdot20 - 15 = 80 - 15 = 65 \checkmark$

LaTeX source of the formulas on this page

\[ 4x - 15 = 65\ \Rightarrow\ x = 20 \]
\[ 4x - 15 = 65 \]
\[ 4x - 15 + 15 = 65 + 15 \ \Rightarrow\ 4x = 80 \]
\[ \frac{4x}{4} = \frac{80}{4} \ \Rightarrow\ x = 20 \]
\[ 4\cdot20 - 15 = 80 - 15 = 65 \checkmark \]

Trying values of x in 4x − 15 = 65

x	4x − 15	Equals 65?
18	57	no
19	61	no
20	65	yes
21	69	no
22	73	no

Questions

What is x in 4x − 15 = 65?

The solution of 4x − 15 = 65 is x = 20.

How do you solve 4x − 15 = 65?

Add 15 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) − 15 = 65, which is 65.

Solve 4x − 15 = 65

How to work it out

Trying values of x in 4x − 15 = 65

Questions

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