Subnumerics with algebra

I have always had a hard time with the basic algebra because I tend to rush and skip parts, but in this case, I also have to deal with figuring out how subnumerics are affected when they cross the equal mark, plus the separation mark (it looks like an equal with arrows pointing in opposite directions. this shows the number separating into ph and nv and has nothing to do with the equal marks)

Also, there is only one way you can use +,-,/,and x with ph and another one, and that is by using its own number. this is an identity