Discover Questions

Could someone help me with these math problems? I can't figure them out. Solve the linear equation;
x+2y=15
y=-2x+0 9x-12y=-3
-12x+16y=4? Does NASA still use miles instead of kilometers? What day will it be exactly 6 months from June 14th, 2017? Best answer gets buncha stars? Questions for medicine I could not get it and I need your help? In one mole of the compound iron(III) oxide,
what fraction of the total number of ions is
the oxygen ion?