Effectively, we replaced x with 4 and then simplified using PEMDAS.
And in the RS column, you'll have these steps
x + 7
4 + 7
11
We get the same thing at the bottom of each column. This shows that we end up with 11 = 11 after simplifying both sides. Therefore, we've confirmed that x = 4 is the solution to 3x - 1 = x + 7
A two story home might use translation to have both floors identical and most homes have windows of the same size and shape so they might also use translation. Sometimes buildings use reflection to make rooms opposite each other the same.