my question is for math,

I have the problem worked out i just don't remember what the tutor who helped me told me for the explanation of steps i just like to know how they came up with that.

Directions: Solve each literal equation for the indicated variable.

A=1/2h(B+b) (for b) Area of trapezoid
A= h(B+b)/2
2A=h(B+b)
2A/h=B+b
2A/h-B=b

A=(1/2h)(B+b) (for b) Area of trapezoid
A= h(B+b)/2 is another way of writing the same thing
2A=h(B+b) Is what ou get by multiplying both sides of the equation by 2.
2A/h=B+b Is what you get by divifing both sides of the equation by h
2A/h-B=b Is what you get by subtracting B from both sides. This provides an equation for b in terms of A, h and B

I appreciate your help very much thank you this way i can do a couple of more problems similar to this one i appreciated i just couldn't remember the explanations.