Step-by-step explanation:
curved surface area =
perimeter of triangular base × length
= 3×8 + 12
= 24 + 12
= 36mm^2
total surface area
= curved surface area + 2× area of triangular base
= 36 + 2 × root3 ×8^2 ÷ 4
= 36 + 2 × root3 × 16
= 36 + 2× 27.71
= 36 + 55. 425
= 91.425 mm^2