Could somebody answer these three questions with simple yet explanatory answers?

This is for #11 and #12. 
First lets find the lateral area of each triangle. We will use the following formula:-    
lateral area = 4 (1/2 * base * slant height)
11. LA = 4 (1/2 * 8 cm * 7.5 cm)          
           = 120 cm^2

12. LA = 4 (1/2 * 14 in * 12in ) =
      LA = 336  cm^2  
   Now lets find the surface area:-  
    surface area = lateral area + area of the base  
   11. S.A. = 120 cm^2 + 8 * 8             
            = 120 cm^2 + 64            
            = 184 cm^2 S.A. = 336 cm^2 + 14 * 14        
   12.     = 336 cm^2 + 196        
             = 532 cm^2  
Lateral Area:-
11. 120 cm^2 
12. 336 cm^2  
 Surface Area:-
11. 184 cm^2
12. 532 cm^2  
   
Hope I helped ya!!