How to write the algebraic expression one number added to another number

In a certain pentagon, the interior angles are a,b,c,d,e where a,b,c,d,e are integers strictly less than 180. ("strictly less than 180" means they are "less than and not equal to" 180.) if the median of the interior angles is 61 and there is only one mode, then what are the degree measures of all five angles?

What is the size of the matrix resulting from

What is the product? a-3/15a × 5/a-3