What's the answer to this problem and how do i work it out?

The formula to finding the Volume of a rectangular prism is  
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  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. 

Letter b hope it

When rates are expressed as a quantity of 1, such as 2 feet per second or 5 miles per hour, they are called unit rates. if you have a multiple-unit rate such as 120 students for every 3 buses, and want to find the single-unit rate, write a ratio equal to the multiple-unit rate with 1 as the second term.