Question 609851
The area of a triangle is {{{ (1/2)*b*h }}}
Call the horizontal part of the roof {{{ 2b }}}
The vertical line from the center of {{{2b}}}
to the top of the roof is {{{ h }}}.
So, the area of the roof is the sum
{{{ (1/2)*b*h + (1/2)*b*h = b*h }}}
Remember that {{{ b }}} is 1/2 of the 
horizontal part of the roof because I
said the whole horizontal part was {{{ 2b }}}