Question

I don't understand... please help...?

Tell whether the product AB is defined for A4x5 and B5x3.

and

Tell whether the product QP is defined for P2x5 and Q5x3.

Answer 1

It seems to me that there should be more to that problem than what you posted.

Answer 2

there isnt, they both just say
"If yes, give the product's dimensions as the following example: 4x3
If no, type no in the box. "

after the question

Answer 3

@FutureMathProfessor got any idea about this?