Simplify -3x^2+2y^2-7+10x^2-12y^2+15

$- 3 x^{2} + 2 y^{2} - 7 + 10 x^{2} - 12 y^{2} + 15$

Add $- 3 x^{2}$ and $10 x^{2}$ .

$7 x^{2} + 2 y^{2} - 7 - 12 y^{2} + 15$

Subtract $12 y^{2}$ from $2 y^{2}$ .

$7 x^{2} - 10 y^{2} - 7 + 15$

Add $- 7$ and $15$ .

$7 x^{2} - 10 y^{2} + 8$