题目计算:(1)3x−2x+5x(1)3x-2x+5x(1)3x−2x+5x；(2)(8m−7n)−3(4m−5n)(2)\left(8m-7n\right)-3\left(4m-5n\right)(2)(8m−7n)−3(4m−5n).知识点：单项式乘多项式章节：数与式 / 整式
