Solve 4x − 15 = 25

The solution of 4x − 15 = 25 is x = 10.

4x - 15 = 25\ \Rightarrow\ x = 10

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The lines y = 4x − 15 and y = 25 meet at x = 10. 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.
$4x - 15 = 25$
2
Add 15 to both sides:
$4x - 15 + 15 = 25 + 15 \ \Rightarrow\ 4x = 40$
3
Divide both sides by 4:
$\frac{4x}{4} = \frac{40}{4} \ \Rightarrow\ x = 10$
4
Check: put x = 10 back into the equation.
$4\cdot10 - 15 = 40 - 15 = 25 \checkmark$

LaTeX source of the formulas on this page

\[ 4x - 15 = 25\ \Rightarrow\ x = 10 \]
\[ 4x - 15 = 25 \]
\[ 4x - 15 + 15 = 25 + 15 \ \Rightarrow\ 4x = 40 \]
\[ \frac{4x}{4} = \frac{40}{4} \ \Rightarrow\ x = 10 \]
\[ 4\cdot10 - 15 = 40 - 15 = 25 \checkmark \]

Trying values of x in 4x − 15 = 25

x	4x − 15	Equals 25?
8	17	no
9	21	no
10	25	yes
11	29	no
12	33	no

Questions

What is x in 4x − 15 = 25?

The solution of 4x − 15 = 25 is x = 10.

How do you solve 4x − 15 = 25?

Add 15 to both sides to get 4x = 40, then divide both sides by 4 to get x = 10.

How do I check the answer?

Replace x by 10: 4(10) − 15 = 25, which is 25.

Solve 4x − 15 = 25

How to work it out

Trying values of x in 4x − 15 = 25

Questions

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