Solve 7x − 15 = 55

The solution of 7x − 15 = 55 is x = 10.

7x - 15 = 55\ \Rightarrow\ x = 10

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The lines y = 7x − 15 and y = 55 meet at x = 10. 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.
$7x - 15 = 55$
2
Add 15 to both sides:
$7x - 15 + 15 = 55 + 15 \ \Rightarrow\ 7x = 70$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{70}{7} \ \Rightarrow\ x = 10$
4
Check: put x = 10 back into the equation.
$7\cdot10 - 15 = 70 - 15 = 55 \checkmark$

LaTeX source of the formulas on this page

\[ 7x - 15 = 55\ \Rightarrow\ x = 10 \]
\[ 7x - 15 = 55 \]
\[ 7x - 15 + 15 = 55 + 15 \ \Rightarrow\ 7x = 70 \]
\[ \frac{7x}{7} = \frac{70}{7} \ \Rightarrow\ x = 10 \]
\[ 7\cdot10 - 15 = 70 - 15 = 55 \checkmark \]

Trying values of x in 7x − 15 = 55

x	7x − 15	Equals 55?
8	41	no
9	48	no
10	55	yes
11	62	no
12	69	no

Questions

What is x in 7x − 15 = 55?

The solution of 7x − 15 = 55 is x = 10.

How do you solve 7x − 15 = 55?

Add 15 to both sides to get 7x = 70, then divide both sides by 7 to get x = 10.

How do I check the answer?

Replace x by 10: 7(10) − 15 = 55, which is 55.

Solve 7x − 15 = 55

How to work it out

Trying values of x in 7x − 15 = 55

Questions

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