Answer:
a)= 2
b) 6.324
c) P= 0.1217
Step-by-step explanation:
a) The mean of the sampling distribution of X`1- X`2 denoted by ux`-x` = u1-u2 is equal to the difference between population means i.e = 2 ( given in the question)
b) The standard deviation of the sampling distribution of X`1- X`2 ( standard error of X`1- X`2) denoted by σ_X`1- X`2 is given by
σ_X`1- X`2 = √σ²/n1 +σ²/n2
Var ( X`1- X`2) = Var X`1 + Var X`2 = σ²/n1 +σ²/n2
so
σ_X`1- X`2 =√20 +20 = 6.324
if the populations are normal the sampling distribution X`1- X`2 , regardless of sample sizes , will be normal with mean u1-u2 and variance σ²/n1 +σ²/n2.
Where as Z is normally distributed with mean zero and unit variance.
If we take X`1- X`2= 0 and u1-u2= 2 and standard deviation of the sampling distribution = 6.324 then
Z= 0-2/ 6.342= -0.31625
P(-0.31625<z<0)= 0.1217
The probability would be 0.1217
Answer: B. 

Step-by-step explanation:
Let
be the proportion of all U.S. adults that smoked in 1995. Let
denote the proportion of all U.S. adults that smoked in 2000.
Objective for the study : Whether the proportion of U.S. adults that smoke declined during the 5-year period between the samples.
i.e. 
Alternative hypothesis
is the statement containing population parameter that shows there is significant difference between the groups being tested.
⇒ 
Null hypothesis
is the statement containing population parameter that shows there is no significant difference between the groups being tested.
⇒ 
Hence, The hypotheses to test in this problem are


Hence, the correct answer is B. 

Like terms are those terms, which have the common variable with same powers.
The number of like terms in the given expression are 3, which is
. the option 3 is the correct option.
<h3>What is like terms?</h3>
In the algebra or the algebraic expression the like terms are those terms, which have the common variable with same powers.
Given information-
The given expression in the problem is,

The given expression is the algebraic expression which 3 number of unknowns variables.
There is total 6 terms in the given expression. In which 5 terms consists the variables and one term is constant.
In the given expression,
- The total number of terms with variable x are 3 which are,
.
- The total number of terms with variable y is 2 which is
.
- The total number of terms with variable z is 1 which is
.
- The total number of constant terms is 1 which is 7.
Thus the number of like terms in the given expression are 3, which is
. the option 3 is the correct option.
Learn more about the like terms here;
brainly.com/question/1779134
RT = RS + ST
8x - 43 = 2x - 4 + 4x - 1
8x - 43 = 6x - 5
8x - 6x = -5 + 43
2x = 38
x = 38/2
x = 19
QS = 2RS = 2(2x-4) = 2(2*19-4) = 2*34 = 68
Answer:
t = 480
Step-by-step explanation:
When we have equations with variables, we always want to isolate the variable, so lets get rid of 4 first.
Add 4 to both sides :
-96 = -t/5
Multiply both sides by the denominator :
-480 = -t
Divide both sides by negative 1 :
t = 480