Maths solutions. Algebra - substitution into a formula

[MrGreensweightHist]

Something not mentions.
Take that formula A = 2r+7
Instead of being given A, you are given that r is 4.5 instead of being given A, and let's be honest, usually you are measuring r and trying to find A
When you sub in the 4.5 for the variable, you must group it with the exponent.

A = 2r+7 becomes A = (2*4.5)+7

While not too important here, there are other math problems where if you don't group them like that, you will get the wrong answer when you start using orders of operations to solve.