Question 15381
{{{(8X^3+16x^2-10)-(5x^3-4x^2+7)}}}
={{{8X^3+16x^2-10-5x^3+4x^2-7}}}
={{{8X^3-5x^3+16x^2+4x^2-10-7}}}
={{{(8-5)x^3+(16+4)x^2-10-7}}}
={{{3x^3+20x^2-17}}}

OK