Solve 7x − 15 = 111

The solution of 7x − 15 = 111 is x = 18.

7x - 15 = 111\ \Rightarrow\ x = 18

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The lines y = 7x − 15 and y = 111 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 subtraction, then the multiplication.
$7x - 15 = 111$
2
Add 15 to both sides:
$7x - 15 + 15 = 111 + 15 \ \Rightarrow\ 7x = 126$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{126}{7} \ \Rightarrow\ x = 18$
4
Check: put x = 18 back into the equation.
$7\cdot18 - 15 = 126 - 15 = 111 \checkmark$

LaTeX source of the formulas on this page

\[ 7x - 15 = 111\ \Rightarrow\ x = 18 \]
\[ 7x - 15 = 111 \]
\[ 7x - 15 + 15 = 111 + 15 \ \Rightarrow\ 7x = 126 \]
\[ \frac{7x}{7} = \frac{126}{7} \ \Rightarrow\ x = 18 \]
\[ 7\cdot18 - 15 = 126 - 15 = 111 \checkmark \]

Trying values of x in 7x − 15 = 111

x	7x − 15	Equals 111?
16	97	no
17	104	no
18	111	yes
19	118	no
20	125	no

Questions

What is x in 7x − 15 = 111?

The solution of 7x − 15 = 111 is x = 18.

How do you solve 7x − 15 = 111?

Add 15 to both sides to get 7x = 126, then divide both sides by 7 to get x = 18.

How do I check the answer?

Replace x by 18: 7(18) − 15 = 111, which is 111.

Solve 7x − 15 = 111

How to work it out

Trying values of x in 7x − 15 = 111

Questions

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