Since they are asking for the unit rate in bolts per wing nut, you can think of it as bolts per ONE wing nut.
To figure that out, you can divide 100 bolts by 2 wing nuts to get 50 bolts per wing nut.
Using parenthesis, we want to add 25 and 9 first before dividing.
170/ (25+9)
She gave them 24 dozens. To answer, you multiply 12x12 which equals 144. Then divide that by 6 and you get 24