y = yearbook club
d = drama club
y + d = 84
d = y + 16
now we sub y + 16 in for d in the first equation
y + d = 84
y + (y + 16) = 84
2y + 16 = 84
2y = 84 - 16
2y = 68
y = 68/2
y = 34 <=== yearbook club students
d = y + 16
d = 34 + 16
d = 50 <=== drama club students