https://www.sciencebuddies.org/science- ... #materials
In the Procedure section of this link, at the bottom, it shows 3 equations. In Equation 1.i it says, "If you are not sure how Equation 2 was derived from Equation 1, take a moment to examine the equations so that you understand the derivation process." I have been trying to figure out how it was derived for many days! Can somebody please help me figure it out? I hate how unspecific that sentence is and how it assumes everyone knows how it was derived!

