Ответ:\(x^2y+xy^2\).\(18xy^2-35x^2y\).\(6a^3b+8a^2c\).\(-120xy^2+28x^2y\).\((11-8+3+1)a^5=7a^5\).\((1.9-2.9-1)x^3=-2x^3\).\((20+5-17)xy=8xy\).\((8-3+1-7)ab^2=-ab^2\).