Find the sum of 8x cube y +2xy cube -18and -12x cube y +7xy cube and subtract it from the sum of 19x cube y -17xy cube +12and -21+5xy cube .? PLEASE SOLVE IT ?????

Answer 1

It is customary to write cube as ^3, i.e. write x³y as x^3y and
xy³ as xy^3.

The problem is then
19x^3y-17xy^3-21+5xy^3-[8x^3y+2xy^3-18 - 12x^3y+7xy^3]

Remove brackets:
19x^3y-17xy^3-21+5xy^3-8x^3y-2xy^3+18-12x^3y-7xy^3
Group like terms and add:
(19-8-12)x^3y+(-17+5-2-7)xy^3+(-21+18)
=-x^3y-21xy^3-3