Solve 9x − 3 = 42

The solution of 9x − 3 = 42 is x = 5.

9x - 3 = 42\ \Rightarrow\ x = 5

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The lines y = 9x − 3 and y = 42 meet at x = 5. 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.
$9x - 3 = 42$
2
Add 3 to both sides:
$9x - 3 + 3 = 42 + 3 \ \Rightarrow\ 9x = 45$
3
Divide both sides by 9:
$\frac{9x}{9} = \frac{45}{9} \ \Rightarrow\ x = 5$
4
Check: put x = 5 back into the equation.
$9\cdot5 - 3 = 45 - 3 = 42 \checkmark$

LaTeX source of the formulas on this page

\[ 9x - 3 = 42\ \Rightarrow\ x = 5 \]
\[ 9x - 3 = 42 \]
\[ 9x - 3 + 3 = 42 + 3 \ \Rightarrow\ 9x = 45 \]
\[ \frac{9x}{9} = \frac{45}{9} \ \Rightarrow\ x = 5 \]
\[ 9\cdot5 - 3 = 45 - 3 = 42 \checkmark \]

Trying values of x in 9x − 3 = 42

x	9x − 3	Equals 42?
3	24	no
4	33	no
5	42	yes
6	51	no
7	60	no

Questions

What is x in 9x − 3 = 42?

The solution of 9x − 3 = 42 is x = 5.

How do you solve 9x − 3 = 42?

Add 3 to both sides to get 9x = 45, then divide both sides by 9 to get x = 5.

How do I check the answer?

Replace x by 5: 9(5) − 3 = 42, which is 42.

Solve 9x − 3 = 42

How to work it out

Trying values of x in 9x − 3 = 42

Questions

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