Solve 12x + 9 = 57

The solution of 12x + 9 = 57 is x = 4.

12x + 9 = 57\ \Rightarrow\ x = 4

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The lines y = 12x + 9 and y = 57 meet at x = 4. 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.
$12x + 9 = 57$
2
Subtract 9 from both sides:
$12x + 9 - 9 = 57 - 9 \ \Rightarrow\ 12x = 48$
3
Divide both sides by 12:
$\frac{12x}{12} = \frac{48}{12} \ \Rightarrow\ x = 4$
4
Check: put x = 4 back into the equation.
$12\cdot4 + 9 = 48 + 9 = 57 \checkmark$

LaTeX source of the formulas on this page

\[ 12x + 9 = 57\ \Rightarrow\ x = 4 \]
\[ 12x + 9 = 57 \]
\[ 12x + 9 - 9 = 57 - 9 \ \Rightarrow\ 12x = 48 \]
\[ \frac{12x}{12} = \frac{48}{12} \ \Rightarrow\ x = 4 \]
\[ 12\cdot4 + 9 = 48 + 9 = 57 \checkmark \]

Trying values of x in 12x + 9 = 57

x	12x + 9	Equals 57?
2	33	no
3	45	no
4	57	yes
5	69	no
6	81	no

Questions

What is x in 12x + 9 = 57?

The solution of 12x + 9 = 57 is x = 4.

How do you solve 12x + 9 = 57?

Subtract 9 from both sides to get 12x = 48, then divide both sides by 12 to get x = 4.

How do I check the answer?

Replace x by 4: 12(4) + 9 = 57, which is 57.

Solve 12x + 9 = 57

How to work it out

Trying values of x in 12x + 9 = 57

Questions

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