Solve 4x − 9 = 55

The solution of 4x − 9 = 55 is x = 16.

4x - 9 = 55\ \Rightarrow\ x = 16

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The lines y = 4x − 9 and y = 55 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.
$4x - 9 = 55$
2
Add 9 to both sides:
$4x - 9 + 9 = 55 + 9 \ \Rightarrow\ 4x = 64$
3
Divide both sides by 4:
$\frac{4x}{4} = \frac{64}{4} \ \Rightarrow\ x = 16$
4
Check: put x = 16 back into the equation.
$4\cdot16 - 9 = 64 - 9 = 55 \checkmark$

LaTeX source of the formulas on this page

\[ 4x - 9 = 55\ \Rightarrow\ x = 16 \]
\[ 4x - 9 = 55 \]
\[ 4x - 9 + 9 = 55 + 9 \ \Rightarrow\ 4x = 64 \]
\[ \frac{4x}{4} = \frac{64}{4} \ \Rightarrow\ x = 16 \]
\[ 4\cdot16 - 9 = 64 - 9 = 55 \checkmark \]

Trying values of x in 4x − 9 = 55

x	4x − 9	Equals 55?
14	47	no
15	51	no
16	55	yes
17	59	no
18	63	no

Questions

What is x in 4x − 9 = 55?

The solution of 4x − 9 = 55 is x = 16.

How do you solve 4x − 9 = 55?

Add 9 to both sides to get 4x = 64, then divide both sides by 4 to get x = 16.

How do I check the answer?

Replace x by 16: 4(16) − 9 = 55, which is 55.

Solve 4x − 9 = 55

How to work it out

Trying values of x in 4x − 9 = 55

Questions

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