Solve 4x − 15 = 13

The solution of 4x − 15 = 13 is x = 7.

4x - 15 = 13\ \Rightarrow\ x = 7

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The lines y = 4x − 15 and y = 13 meet at x = 7. 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.
$4x - 15 = 13$
2
Add 15 to both sides:
$4x - 15 + 15 = 13 + 15 \ \Rightarrow\ 4x = 28$
3
Divide both sides by 4:
$\frac{4x}{4} = \frac{28}{4} \ \Rightarrow\ x = 7$
4
Check: put x = 7 back into the equation.
$4\cdot7 - 15 = 28 - 15 = 13 \checkmark$

LaTeX source of the formulas on this page

\[ 4x - 15 = 13\ \Rightarrow\ x = 7 \]
\[ 4x - 15 = 13 \]
\[ 4x - 15 + 15 = 13 + 15 \ \Rightarrow\ 4x = 28 \]
\[ \frac{4x}{4} = \frac{28}{4} \ \Rightarrow\ x = 7 \]
\[ 4\cdot7 - 15 = 28 - 15 = 13 \checkmark \]

Trying values of x in 4x − 15 = 13

x	4x − 15	Equals 13?
5	5	no
6	9	no
7	13	yes
8	17	no
9	21	no

Questions

What is x in 4x − 15 = 13?

The solution of 4x − 15 = 13 is x = 7.

How do you solve 4x − 15 = 13?

Add 15 to both sides to get 4x = 28, then divide both sides by 4 to get x = 7.

How do I check the answer?

Replace x by 7: 4(7) − 15 = 13, which is 13.

Solve 4x − 15 = 13

How to work it out

Trying values of x in 4x − 15 = 13

Questions

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