The measure of B’C’ is 18 inches
The plane PRS passes through the points P, R and S. So it contains the line RS. Also the plane QRS passes through the points Q, R and S. So it contains the line RS as well. Since both the planes contain the line RS, the line RS must be the intersection of plane PRS and QRS
He did not divide his milligrams by the proper factor. He treated it as if it were only kilograms. He should have divided by a million.
The answer is D. The +1 refers to the extra cup leftover from a previous bag. X represents how many cups are in each bag, and that is what you need to know. The three represents how many bags she bought, and the 25 represents how many cups of birdseed she had overall.
Hopefully this helps!