Question 84811
Ok, for the 1st one it seems like you want to solve for the small b, so thats what we are going to do

{{{A=(1/2)h (B+b)}}} 

First step is to get (B+b) by itself, to do this we 1st multiply both sides by 2 to get:

{{{2A=h (B+b)}}} 

Second to again get (B+b) by itself on one side, we divide both sides by h to get:

{{{2A/h=(B+b)}}}

Finally we subtract B from both sides to get:

{{{2A/h - B =b}}}

For the second part we can begin by simplfying. To do this, we will first find 1/2 of 16 so the equation will look like:

{{{A=8 (20+b)}}}

Then we can distribute the 8 into the parenthesis to get:

{{{A=160+8b}}}

Next step would be to subtract 160 from both sides to get:

{{{A-160=8b}}}

Finally we would divide both sides by 8 to get b by itself:

{{{ (A-160)/8=b }}}