the diagram shows a solid metal cuboid. The areas of three of the faces are marked on the diagram. the lengths in cm, of the edges of the cuboid, are whole numbers. The metal cuboid is melted and made into cubes. Each cube has side lengths of 2.5cm. Work out the greatest number of cubes that can be made.

answer:

your answer is: c. 196 7/8 in^3.

this may not be at all, but i use the same website you're using for school, and if i'm stuck doing one of these i try to look for it on the section.

let x and 400 - x be the two numbers.  

==> 0.80x + 0.85(400 - x) = 400 - 68 from the statement of the problem.  

< ==> 0.80x + 0.85(400 - x) = 400 - 68  

==> 340 - 0.05x = 332  

< ==> -0.05x = -8 ==> x = 160, the first number ==> 400 - x = 240, the second number.