Solve 4x − 3 = 21

The solution of 4x − 3 = 21 is x = 6.

4x - 3 = 21\ \Rightarrow\ x = 6

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The lines y = 4x − 3 and y = 21 meet at x = 6. 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.
$4x - 3 = 21$
2
Add 3 to both sides:
$4x - 3 + 3 = 21 + 3 \ \Rightarrow\ 4x = 24$
3
Divide both sides by 4:
$\frac{4x}{4} = \frac{24}{4} \ \Rightarrow\ x = 6$
4
Check: put x = 6 back into the equation.
$4\cdot6 - 3 = 24 - 3 = 21 \checkmark$

LaTeX source of the formulas on this page

\[ 4x - 3 = 21\ \Rightarrow\ x = 6 \]
\[ 4x - 3 = 21 \]
\[ 4x - 3 + 3 = 21 + 3 \ \Rightarrow\ 4x = 24 \]
\[ \frac{4x}{4} = \frac{24}{4} \ \Rightarrow\ x = 6 \]
\[ 4\cdot6 - 3 = 24 - 3 = 21 \checkmark \]

Trying values of x in 4x − 3 = 21

x	4x − 3	Equals 21?
4	13	no
5	17	no
6	21	yes
7	25	no
8	29	no

Questions

What is x in 4x − 3 = 21?

The solution of 4x − 3 = 21 is x = 6.

How do you solve 4x − 3 = 21?

Add 3 to both sides to get 4x = 24, then divide both sides by 4 to get x = 6.

How do I check the answer?

Replace x by 6: 4(6) − 3 = 21, which is 21.

Solve 4x − 3 = 21

How to work it out

Trying values of x in 4x − 3 = 21

Questions

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