Yes a factor is less then the number and the multiple it greater, for example 6 a multiple is 12,24, and so on...
To find Vanilla for ages 8-12, you add up the known amount from each flavor for that age group and subtract it from the total to get... 50 - (25 + 12) = 13
To find Chocolate for ages 13-17, you add up the amount of people know to pick up late and subtract it from the total amount of people who picked chocolate to get... 100 - (35 + 25) = 40
Now that we have that number, we can use it to find the amount of people ages 13-17 who chose Vanilla. To find this you subtract the total amount of people who chose chocolate and strawberry from the total amount of people to get... 80 - (40 + 12) = 28
This should help :)
It's 24k-6
By order of operations, you do the multiplication first: 3k(4) = 12k
12k-6+12k now combine like terms
24k-6
Hope that helps