I suppose a DJ wants to select 4 different songs, then there are: 12*11*10*9 = 11880 ways to choose them.
If the order of the songs he plays doesn't matter, there are:
ways to choose them.
This is how you answer number 15 and 16
We have that
<span> |x+6| >= 5
step 1
resolve for (x+6)>=5------> x>=5-6-------> x>= -1
the solution is the interval </span>(-1, ∞)
<span>
step 2
resolve for -(x+6) >=5------> -x-6 >=5----> -x >= 5+6---> -x>=11----> x<=-11
</span>the solution is the interval (-∞, -11)
<span>
using a graph tool
see the attached figure
the solution is the interval (-</span>
∞, -11) ∩ (-1, ∞)
You can do 15-5=10 and then you have 3 left to subtract. Which means 10-3=7
Y=4x-1 because it can be the only one