Which problem can be solved using this equation? (explain)

x + 2 = (42)?

a.) mary had 42 empty boxes when she started packing yesterday. today, she is 2 short of having 1/4 of the boxes filled. how many boxes are filled?

b.) mary had 42 empty boxes when she started packing yesterday. today, she is 2 short of having 1/4 of the boxes filled. how many boxes are still empty?

c.) mary had 42 empty boxes when she started packing yesterday. today, she is 2 short of having 1/4 of the boxes filled. how many additional boxes does mary need?

d.) mary had 42 empty boxes when she started packing yesterday. today, she is 2 short of having 1/4 of the boxes filled. how many boxes will mary have left to fill tomorrow?

A).  Mary had 42 empty boxes when she started packing yesterday.
Today, she is 2 short of having 1/4 of the boxes filled.
How many boxes are filled?

Total number of boxes . . . 42
1/4 of them. . . . . . . . . . . . . 1/4(42)
Does she have that many filled today ?
NO !  She does not have  1/4(42)  filled today.
She has  2  less than that filled. . . .  1/4(42) - 2

What is the number she has filled ?   Call it 'x' .

                                 It's    x = 1/4(42) - 2

Add  2  to each side:     x + 2 = 1/4(42)            

Well gosh !  That's the equation in the question.
We were able to build it with the story in Choice-A.
You can't do that with any of the other choices.  

How many does she have filled ?

                                       x  =  1/4(42) - 2

                                           =  10.5  -  2

                                           =     8.5 boxes .

Is this some kind of a trick question ?  What does this mean ?
How can she have half of a box filled ?     
The box has to be either full or not full.
I mean, a box can be half-full, but there's no such thing as a half-box that's full. 
What answer do they want ?

Should we say:  She has 8 boxes filled ... plus a full half-box ?
What's a full half-box ? ?

Should we say:  She has 8 and 1/2 boxes filled  ?
I don't know.  That last piece isn't a filled box.

The Math is done.  What's left is Philosophy and Semantics.
That's more than I can handle.

Maybe it's just a sloppily-written question.
Everything would be much easier if she started with 40 boxes or 44 boxes.
I think you can point out the sloppiness to your teacher and have a discussion.

The lateral side of a triangular pyramid is a triangle. in order to increase the lateral surface area, the slant height and the height should be altered