Explanation:
x = number of novels
y = number of dictionaries
x = 8y
88x + 208y = 13680
now, using the identity of the first equation in the second equation gives us
88(8y) + 208y = 13680
704y + 208y = 13680
912y = 13680
y = 13680/912 = 15
x = 8y = 8×15 = 120
so, there were 120 novels and 15 dictionaries sold.