A triangular prism is 17 inches long and has a triangular face with a base of 18 inches and a height of 12 inches. The other two sides of the triangle are each 15 inches. What is the surface area of the triangular prism?

1. ∠1 is complementary to ∠2 and ∠3 is complementary to ∠2. subtraction property of equality 2. m∠1 + m∠2 = 90 and m∠3 + m∠2 = 90 substitution 3. m∠1 + m∠2 = m∠3 + m∠2 definition of complementary 4. m∠1 = m∠3 given