Solve 3x + 9 = 63

The solution of 3x + 9 = 63 is x = 18.

3x + 9 = 63\ \Rightarrow\ x = 18

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The lines y = 3x + 9 and y = 63 meet at x = 18. 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 addition, then the multiplication.
$3x + 9 = 63$
2
Subtract 9 from both sides:
$3x + 9 - 9 = 63 - 9 \ \Rightarrow\ 3x = 54$
3
Divide both sides by 3:
$\frac{3x}{3} = \frac{54}{3} \ \Rightarrow\ x = 18$
4
Check: put x = 18 back into the equation.
$3\cdot18 + 9 = 54 + 9 = 63 \checkmark$

LaTeX source of the formulas on this page

\[ 3x + 9 = 63\ \Rightarrow\ x = 18 \]
\[ 3x + 9 = 63 \]
\[ 3x + 9 - 9 = 63 - 9 \ \Rightarrow\ 3x = 54 \]
\[ \frac{3x}{3} = \frac{54}{3} \ \Rightarrow\ x = 18 \]
\[ 3\cdot18 + 9 = 54 + 9 = 63 \checkmark \]

Trying values of x in 3x + 9 = 63

x	3x + 9	Equals 63?
16	57	no
17	60	no
18	63	yes
19	66	no
20	69	no

Questions

What is x in 3x + 9 = 63?

The solution of 3x + 9 = 63 is x = 18.

How do you solve 3x + 9 = 63?

Subtract 9 from both sides to get 3x = 54, then divide both sides by 3 to get x = 18.

How do I check the answer?

Replace x by 18: 3(18) + 9 = 63, which is 63.

Solve 3x + 9 = 63

How to work it out

Trying values of x in 3x + 9 = 63

Questions

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