3x^2-{7x-(4x-3)-2x^2}
=3x^2-[7x-4x+3-2x^2]
=3x^2-[3x+3-2x^2]
=3x^2-3x-3+2x^2
=5x^2-3x-3
=5*(-1)^2-3*(-1)-3
=5+3-3
=5