Part 1: Volume of Rectangular Prism
V_rectangular = length x width x height
V_rectangular = 45cm x 17cm x 20cm
V_rectangular = 15300 cm^3
Part 2: Volume of Triangular Prism
V_triangular = (1/2) x base x height x height
V_triangular = (1/2) x 17cm x 18cm x 18cm
V_triangular = 2754 cm^3
Part 3: Total Volume of the Composite Figure
V_total = V_rectangular + V_triangular
V_total = 15300 cm^3 + 2754 cm^3
V_total = 18054 cm^3
Therefore, the total volume of the composite figure is 18054 cm^3.