The surface area of this prism consists of:
Sprism = Sprism + Ssides
the bases of triangles the area of each one is
Atriangle = 1/2bh
Aonebases = 1/2bh
Abothbases = 2×1/2×bh = bh
Arectangle = l×w where l is the length and w is the width
Aside = ls
If the triangular base has unequal sides then you calculate the perimeter( P) of the triangle and multiply it by the height of the prism to get the area of the sides (lateral surface area)
If the base is an equilateral triangle then all three sides have equal areas and the lateral surface area becomes = 3ls
Sprism = bh+pl