The surface area of a triangular prism is \( S.A. = 2B + (S_1 + S_2 + S_3) \), where \( B \) is the area of the triangular base, and \( S_1, S_2, S_3 \) are the areas of the three rectangular lateral faces. The first blank is "2B" and the second blank is "+".
So the complete formula is: \( S.A. = 2B + (S_1 + S_2 + S_3) \)