Question

How do you solve `8=r-5`?

Answer 1

`color(green)(r=13)`

Explanation:

Given
`color(white)("XXX")8=r-5`

Remember that you can add the same amount to both sides of an equation and still maintain the validity of the equation.
`color(white)("XXX")8color(red)(+5)=r-5color(red)(+5)`
or
`color(white)("XXX")13 = r`

Also remember that `b=a` means `a=b`
So
`color(white)("XXX")13 = r` means `color(green)(r=13)`