Let, the number = x
It would be: 13 + 2x + 7 = 6x
2x+20 = 6x
6x-2x = 20
4x = 20
x = 20/4
x = 5
In short, Your Answer would be 5
Hope this helps!
The answer is r = 40 because 40 divided by 10 = 4
There are two ways to find the total with tax
Either you can do
cost + cost x tax rate
or
cost x (1+tax rate)
Since the second one requires less steps, it's easier to do that.

The cost with tax is
$17.27
Multiple factor product divisor and dividend