The jones family drove to kankakee in 5 hours and returned in 4 hours. their rate on the return trip was 9 mph faster than their rate going. find their rate going?

36 mph

Step-by-step explanation:

Let

D be the distance covered in on trip

x be the rate on return

y be the going rate

if the Jones family drove to Kankakee in 5 hours and returned in 4 hours.

y = D/5 and x = D/4

D = 5y and D = 4x

5y = 4x Equation 1

Their rate on the return trip was 9 mph faster than their rate going

x = y + 9  Equation 2

substitute into equation 1

5y = 4(y + 9)

5y = 4y + 36

collect like terms

5y - 4y = 36

y = 36 mph

The z-score is given by the formula:
z=(x-μ)/σ
μ=1252
σ=129
The answer to the questions given will be as follows:
a] what is the probability that a randomly selected bag contains between 1100 and 1400 chocolate​ chips?
z=(1400-1252)/129
z=1.15625
P(x≤1400)=0.8770

z=(1100-1252)/129
z=0.1190
P(X≤1100)=0.1190

the answer will be:
P(1100≤x≤1400)=0.8770-0.1190=0.758

b]what is the probability that a randomly selected bag contains fewer than 1000 chocolate​ chips? 
z=(1000-1252)/129=-1.954
P(X≤1000)=0.0256

c] what proportion of bags contains more than 1200 chocolate​ chips?
z=(1200-1252)/129
z=-0.4031
P(X≥1200)=1-P(X≤1200)=1-0.4031=0.5969