addign trinomials (2x+4xy+8z)+(8x+5xy+23z) all you have to do is combine the like terms 2x and 8x= 10x, 4xy+5xy=9xy, and 8z+23z=31z. so the simplified answer to adding the trinomials would be 10x+9xy+31z.
Subtacting trinomials (4x+9y+3) - (-1+3x-2y) .
When doing subtracting you still combine like terms but this time you change the sign before every term. If that is confusing, just pretend there is a negative 1 infront of parenthases and multiply that before you subtracts the two trinomials. so...
4x - 3x= x, 9y+2y=11y and 3+1=4. so simplified answer of the subtraction would be x+11y+4
I hope this helped :) Good luck !