Did you take a lot of college level math courses? I too remember feeling like it was really tedious doing all the steps to rearrange an equation when I already knew the solution before I picked up my pencil. But that's all algebra is: the art of rearranging equations. I know what you mean, simple formulas like the ones above are frustrating because they're easy with to solve without any manipulation, but that's just the foundation where you gotta start. In later courses like calculus the math gets complicated enough that there's simply no getting it at a glance, it has to be rearranged and broken down in stages until you get to something like the formula above. Personally, if I hadn't learned those skills through doing the boring show-your-work-even-though-it's-trivia types of problems, I either would've figured it out on my own in later courses or washed out.