Problem one:

I have tried this over and over again but i keep getting answers like 12=12 in the end. Solve the system of equations:

6x-10y=12

-15x+25y=-30

Problem two:

I never really learned this before. Factor:

16x²y²+22xy-3

Problem three:

Never really learned this either. Graph:

y=2x²+5x-12

Thanks for the help in advance =)