7.
lateral surface area of traingular prism=perimeter of traingle ×length=[5+3+4]×6=72cm²
curved surface area=2[area oftraingle]=2×1/2×4×3
=12cm²
now
total surface area=72cm²+12cm²=84cm²
8.
volume of traingular prism=area of traingle ×length
=1/2×12×3.4×4=81.6in³