My answers wrong - simplify by combining like terms

19) you have to look for similar terms

you can see there is more than one term with y^2 in it

-3y^2 - 5y^2

= -8y^2

there is also more than one 'z' term

3z-5z = -2z

dont forget about the 4x^2 and put it together

answer = 4x^2 - 8y^2 - 2z

i think you got confused because of the way you laid out your working??

next time identify the like terms and try working them out seperately first

Your maths is very weak try yourself this would improve your skills don't depend on others