[tex](5a^{2}+2a-3b)-(3a^{2}+7a+6b)=5a^{2}+2a-3b-3a^{2}-7a-6b=2a^{2}-5a-9b[/tex]
[tex](2pq-5p+3q)-(6pq-2q)=2pq-5p+3q-6pq+2q=-4pq-5p+5q[/tex]
[tex](-x^{2}+3y)-(3y+3x^{2}-2xy)=-x^{2}+3y-3y-3x^{2}+2xy=-4x^{2}+2xy[/tex]
