Answer: 8 
hours
Step-by-step explanation:
Let x represent the time it takes if both are used.
The unit time it takes to fill the pool using the first house is 1/20 and also the unit time it takes to fill the pool using the second house is 1/16 , therefore:
1/16 + 1/20 = 1/x
= 
=
Therefore
x = 
Therefore, it takes 8 hours using both houses
The surface area (SA) of a rectangular prism (box) is obtained by the equation,
SA = 2 (LW + WH + LH)
where L is length, W is width, and H is height.
Substituting the values for the dimensions,
SA = 2 (15cm x 22cm + 22cm x 9cm + 15cm x 9 cm) = 1326 cm²
Thus, the surface area of the box is 1326 cm².
Answer: the fourth option; all the real values except x = 7 and the x for which f(x) = - 3
Explanation:
1) the composed function (g ° f) )x= is the application of the function g (x) to the function f(x), this is you first apply f(x) and then apply g(x): g [f(x) ]
2) So the domain is the set of values for which f(x) is defined and then those values of f(x) for which g(x) is defined.
3) The values of x for which f(x) is defined is all the real values except x = 7.
4) The values of f(x) for which g(x) is defined are all the values of f(x) except f(x) = - 3.
5) So, the domain of the composed function is all the real values except x = 7 and the x for which f(x) = - 3
6) Important remark: notice that there is an error in the statements listed, because saying that the domain is all the real values except x ≠ 7 and f(x) ≠ - 3 means that tha domain is only x = 7 and f(x) = - 3, when what they meant was that the composed function is not defined for x = 7 and f(x) = - 3 (this is a bad use of double negation which is a good expample of why double negation must be avoided).
