Langston has $45$ greeting cards. He gives $18$ of the cards to his friends. What percent of his greeting cards does he give to his friends?

Will mark 50 show all what is the solution to the system of equations? use the substitution method and show your work. -5x+y= -3 -15 x+3y=7 explain what your answer in part (a) tells you about the association of the lines in this system.