We have to calculate the volume of the rectangular prisms:
Volume of a rectangular prism: Length x width x height
Terrarium 1:
V1 = 40 x 25 x20 = 20,000 cm3
Terrarium 2:
V2= 25 x 30 x 20 = 15,000 cm3
Add both volumes:
V1+V2 = 20,000+15,000 = 35,000 cm3