Step-by-step explanation:
(a+b)(ab)

Answer:
230
Step-by-step explanation:
20x11=220
20x0.5=10
220+10=230
Answer:
b. 2.333
Step-by-step explanation:
Test if the mean transaction time exceeds 60 seconds.
At the null hypothesis, we test if the mean transaction time is of 60 seconds, that is:

At the alternate hypothesis, we test if it exceeds, that is:

The test statistic is:

In which X is the sample mean,
is the value tested at the null hypothesis, s is the standard deviation of the sample and n is the size of the sample.
60 is tested at the null hypothesis:
This means that 
A sample of 16 ATM transactions shows a mean transaction time of 67 seconds with a standard deviation of 12 seconds.
This means that 
Value of the test statistic:




Thus, the correct answer is given by option b.
Answer:
(x, y)=(4,-8)
Step-by-step explanation:
9x+y=28
3x+3y=-12 /:(-3)
9x+y=28.......(1)
-x-y=4......(2)
9x+y=28
(1)+(2): 8x=32
9x+y=28
x=32/8
9x+y=28
x=4
9*4+y=28
x=4
36+y=28
x=4
y=28-36
x=4
y=-8
x=4
(x, y) =(4,-8)