Answer:
x=-9
Step-by-step explanation:
x+5=2(7+x)
x+5=14+2x
x-2x=14-5
-1x=9
x=-9
Answer:
The minimum sample size needed is 125.
Step-by-step explanation:
In a sample with a number n of people surveyed with a probability of a success of 
, and a confidence level of 
, we have the following confidence interval of proportions.
In which
z is the zscore that has a pvalue of 
.
The margin of error is:
For this problem, we have that:
99% confidence level
So 
, z is the value of Z that has a pvalue of 
, so 
.
What minimum sample size would be necessary in order ensure a margin of error of 10 percentage points (or less) if they use the prior estimate that 25 percent of the pick-axes are in need of repair?
This minimum sample size is n.
n is found when 
So
Rounding up
The minimum sample size needed is 125.
X is the number of songs and Y the number of pics
our 2 equations will be - X+y=11 & 4x+2y=24
consider x=11-y
Lets replace x in 2:
=4(11-y) +2y=24
=44-4y+2y=24
=44-24= 4y-2y
=20= 2y
=Y=20/2
=Y=10
Lets replace y in 1
=X+10=11
=X=11-10
=X=1
To learn more about equations from the given link
brainly.com/question/269374
#SPJ4
Answer:
System of equations:
20x + 30y = 650
x + y = 25
Time underwater = 10 hours
Time at the surface = 15 hours
Step-by-step explanation:
Let x = time underwater at 20 km/h.
Let y = time on the surface at 30 km/h.
speed = distance/time
distance = speed * time
distance underwater: 20x
distance on the surface: 30y
total distance: 650
20x + 30y = 650
total time: x + y
total time: 25
x + y = 25
20x + 30y = 650
x + y = 25
20x + 30y = 650
-20x - 20y = -500
--------------------------------
10y = 150
y = 15
x + y = 25
x + 15 = 25
x = 10
