Question

S=45,р=28см,а в=? что это?

Answer 1

S-- это площадь
P--это периметр
ав- это стороны

Answer 2

A=9 b=5
S=a×b 45=9×5
P=2(a+b) 28=2(9+5)

Answer 3

It seems like you have provided some variables without specifying what they represent. From the information given, it's not clear what "S," "р," "см," and "а в" stand for. In order to assist you accurately, I need more context or a clear explanation of what these variables represent or the context of the problem you are trying to solve. Please provide more details, and I'll do my best to help you with your question.