Solve 6x − 15 = 105

The solution of 6x − 15 = 105 is x = 20.

6x - 15 = 105\ \Rightarrow\ x = 20

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The lines y = 6x − 15 and y = 105 meet at x = 20. 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.
$6x - 15 = 105$
2
Add 15 to both sides:
$6x - 15 + 15 = 105 + 15 \ \Rightarrow\ 6x = 120$
3
Divide both sides by 6:
$\frac{6x}{6} = \frac{120}{6} \ \Rightarrow\ x = 20$
4
Check: put x = 20 back into the equation.
$6\cdot20 - 15 = 120 - 15 = 105 \checkmark$

LaTeX source of the formulas on this page

\[ 6x - 15 = 105\ \Rightarrow\ x = 20 \]
\[ 6x - 15 = 105 \]
\[ 6x - 15 + 15 = 105 + 15 \ \Rightarrow\ 6x = 120 \]
\[ \frac{6x}{6} = \frac{120}{6} \ \Rightarrow\ x = 20 \]
\[ 6\cdot20 - 15 = 120 - 15 = 105 \checkmark \]

Trying values of x in 6x − 15 = 105

x	6x − 15	Equals 105?
18	93	no
19	99	no
20	105	yes
21	111	no
22	117	no

Questions

What is x in 6x − 15 = 105?

The solution of 6x − 15 = 105 is x = 20.

How do you solve 6x − 15 = 105?

Add 15 to both sides to get 6x = 120, then divide both sides by 6 to get x = 20.

How do I check the answer?

Replace x by 20: 6(20) − 15 = 105, which is 105.

Solve 6x − 15 = 105

How to work it out

Trying values of x in 6x − 15 = 105

Questions

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