4. 150 Students were surveyed on how many text messages they send in a day from different devices. Let × represent the number of students using each type of device, cell phone, Chromebook or other.

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.