The formula to finding the Volume of a rectangular prism is [tex]V=(w)(h)(l)[/tex]
W=width L=length H=height
You have 3 rectangular prisms, you need to find the volume of each one and add them together.
(Going from left to right in rectangular prisms)
(3ft x 2ft x 2.5 ft) + (3ft x 1.75ft x 3ft) + (4ft x 4ft x 2.5ft) = Your answer
I hope this helps :)
(Also, You don't need to use the formula as directly stated, the way I showed for your problem is [tex]V=(l)(h)(w)[/tex] As long as you don't multiply the wrong numbers together{as in mixing up the #s from other rectangular prisms} you should be perfectly fine (: )
Comment if you have anymore questions.