WHAT IS THE GROUP of Atom
THAT CANNOT EXIST SEPERATELY​

Question and answers are in the attached picture. you so much in advance.

Find the solution of system of equation y= x-4 y=4x+2

Lance lived in portugal and brazil for a total of 14 months to learn portuguese. he learned an average of 130 new words per month when he lived in portugal, and an average of 150 new words per month when he lived in brazil. in total he learned 1920 new words. write a system of equations to represent the situation. use x to represent portugal, and y to represent brazil