That's the smart way to do math. I mean not with such small numbers but you'd do the same thing adding up large numbers, you break down the numbers and rearrange them in a way that's easier to compute.
Algebra probably feels intuitive to you.
They're also trying to teach that in math classes (it gets called "new" math) but the boomers are freaking out because "why can't they just do normal additions like we used to, this is so complicated". And the answer to that is, 99% of the time you'll be doing algebra because we literally all carry a calculator in our pockets and sometimes on our wrists at all times and we never need to just do a long division. And that kind of thinking really makes it easy to break down formulas because your brain thinks in terms of moving stuff around in an equation.