Concept:We need to find the coefficient of xy in the expression m−n. First, expand both m and n using the distributive property, then subtract the polynomials and identify the xy term.Explanation:Expand m=(3x+4y)(2x+3y):m=3x(2x+3y)+4y(2x+3y)=6x2+9xy+8xy+12y2=6x2+17xy+12y2.Expand n=(x−y)(3x+5y):n=x(3x+5y)−y(3x+5y)=3x2+5xy−3xy−5y2=3x2+2xy−5y2.Now find m−n:m−n=(6x2+17xy+12y2)−(3x2+2xy−5y2)=3x2+(17−2)xy+(12+5)y2=3x2+15xy+17y2.The coefficient of xy in m−n is 15.Answer:15 (Option A)