1) For the area, think of the L shape as a rectangle with another rectangle cut out. The big rectangle is 25x30, and 25x20 was cut out. (The 20 I found as 25-5). So the area is 25x30 - 25x20 = 250 cm^2
The perimeter is all sides added. 25+5+30+25+5 = 90 cm.
I'm sure you can figure out the other ones in the same way!