$1/-13ab+ba-8ab \\=ab(-13+1-8) \\=ab.(-20) \\2/42xy^2.\bigg(\dfrac{1}{2}\bigg)^2xy \\=42xy^2.\dfrac{1}{4}.xy \\=\dfrac{21}{2}.x^2y^3 \\3/\dfrac{80xy^2}{-44x^3yz} \\=\dfrac{-20y}{x^2z} \\4/(-15x^2y^3-10x^3y^3+6xy).5xy \\=-75x^3y^4-50x^4y^4+30x^2y^2 \\5/(3x-2)^2\\=9x^2-12x+4$