Agirl asks her father how many ties he has and he answers with a riddle: "seven-eighths of my ties plus four."

What he's saying is that 7/8 of his ties + 4 ties = all of his ties.
7/8x + 4 = x
Thus, 4 is 1/8 of his ties.
4 = 1/8x
So you simply multiply 4 by 8 to get 32 ties.
32 = x
To check, plug 32 back into the original equation:
7/8(32) + 4 = (32)
28 + 4 = 32
It works!
Hope that helps.