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!!