Make a the subject of: (a+3)=(2a+7)/r

Equation: a+3 = (2a+7)/r

First, we want to rearrange the equation, so that the 'r', which is the denominator of the right hand side, multiplies with (a+3), creating r(a+3) = 2a+7. Expanding this out, the equation becomes ra+3r = 2a+7. We want 'a' to be the subject of this equation and hence we move all the components of the equation with the 'a' variable to one side, and all those without to the other, resulting in: ar-2a = 7-3r. Now, we can factorize 'a', resulting in: a(r-2) = 7-3r, and finally rearrange the equation so that only the a is on the left side side, by dividing the entire equation by (r-2). Hence the result will be: 

a = (7-3r) / (r-2)

Anything unclear in this? This will be a bit easier to see when written out properly, rather than in a paragraph.