Well... all u have to do is 85 divided by 4 which equals 21.25..... unless there is another part of the question!!
15. x ≤ -24
x + 19 ≤ -5
x ≤ -24
16. z > -12
3z > -36
z > -12
17. 185 + c > 410; c > 225
18. C.
x - 6 ≥ 1
x ≥ 7

Please consult the "Calculations" section of this ans .

The information we're given is below :
- slope : -1/3
- Point crossed by the line : (3, 6)
As per given information , we can do the following :
- Write the line's equation in point slope form
Point - slope form looks like so :
y-y₁=m(x-x₁)
y-6=-1/3(x-3)
y-6=-1/3x+1
y=-1/3x+1+7
y=-1/3x+6
↑ 

Let's actually find the line of best fit...
m=(nΣyx-ΣyΣx)/(nΣx^2-ΣxΣx)
m=(11*836-130*55)/(11*385-3025)
m=2046/1210
m=93/55
b=(Σy-93Σx/55)/n
b=(55Σy-93Σx)/(55n)
b=(7150-5115)/(55*11)
b=185/55, so the line of best fit is:
y=(93x+185)/55
A) The approximate y-intercept (the value of y when x=0) is 185/55≈3.36.
Which means that those who do not practice at all will win about 3.36 times
B) y(13)=(93x+185)/55
y(13)≈25.34
So after 13 months of practice one would expect to win about 25.34 times.