Answer:

Step-by-step explanation:
I'm assuming you are trying to find m. In order to do so, you need to get m on one side.
Before doing that let's multiple -2 and -3m by 

add
to both sides

I would get rid of the fraction so I'd multiply both sides by 


divide both sides by -12m

which can be simplified to

ALL UNLESS THAT
IS A POWER
You are correct in thinking that the columns of the first matrix must match with the rows of the second matrix.
So for example, we can multiply a 1 x 5 matrix with a 5 x 7 matrix. The two matching '5's are directly what make multiplication possible in this case. For your problem, the first two '3's match and multiplication is possible.
The rows of the first matrix don't need to match with the columns of the second matrix.
It would be 250 cu. ft.
Say the larger box measures 10x10x20 which would give you a volume of 2,000 cu. ft. The smaller box then would measure half of those lengths or 5x5x10 which would be 250 cu. ft.
Answer:
gallon of milk it is the correct ans