Marking Brainliest. Can someone please how to do this with a fairly simple explanation? I'm not sure what to do.

Explanation:
In the LS column, you'll have these steps
3x - 1
3*4 - 1
12 - 1
11
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