Question 775063
Without the rendering tags,  A=2*pi*r*x+pi*r^2.
With the rendering tags triple left braces and triple right braces, {{{ A=2*pi*r*x+pi*r^2}}}


Make all terms containing x on one side and all other terms on the other side; divide or multiply as appropriate to isolate just x.


PROCESS:
Additive Inverse of {{{pi*r^2}}}.
Multiplicative Inverse of {{{2*pi*r}}}.
Simplify.