Question

(-8y²-12y+5)+(7y²-8)

Answer 1

$(-8y^{2} -12y+5)+(7y^{2} -8)=$
$y^{2} -12y-3$

Answer 2

veja...

$-8y^2-12y+5+(7y^2-8)= \\ \\ -8y^2-12y+5+7y^2-8= \\ \\ -8y^2+7y^2-12y+5-8= \\ \\ -y^2-12y-3$