1)
[tex](3x+10)(4x-10)-(2x-10)(6x+10)=\\\\=12x^2-30x+40x-100-(12x^2+20x-60x-100)=\\\\=12x^2+10x-100-(12x^2-40x-100)=\\\\=12x^2+10x-100-12x^2+40x+100=\\\\=12x^2-12x^2+10x+40x-100+100=\boxed{50x}[/tex]
2)
[tex](y-8)(2y-7)-(5y-3)(y-6)=\\\\=2y^2-7y-16y+56-(5y^2-30y-3y+18)=\\\\=2y^2-23y+56-(5y^2-33y+18)=\\\\=2y^2-23y+56-5y^2+33y-18=\\\\=2y^2-5y^2-23y+33y+56-18=\boxed{-3y^2+10y+38}[/tex]
