Im gonna take an educated guess on this. for the first part only one element has an outershell filled completely. but if they want two elements put chlorine. to lose electrons is probably helium to gain is magnesium. and the last one is lithium and helium because they're small and don't have allot of atomic mass
Substitute the value for y as 450
450=-5x+1
Solve for x
450-1=-5x
449=-5x
89.8=-x
x=-89.8
