Answer:
1120 combinations of four teachers include exactly one of either Mrs. Vera or Mr. Jan.
Step-by-step explanation:
The order in which the teachers are chosen is not important, which means that the combinations formula is used to solve this question.
Combinations formula:
is the number of different combinations of x objects from a set of n elements, given by the following formula.
In this question:
1 from a set of 2(Either Mrs. Vera or Mr. Jan).
3 from a set of 18 - 2 = 16. So

1120 combinations of four teachers include exactly one of either Mrs. Vera or Mr. Jan.
If the first set began to increase, than the other set tends to decrease.
Answer:
B.the total charge before applying sales tax
Step-by-step explanation:
Answer:
C
C=2πR
circumference equals two times pi times radius
Answer:
tenths place
Step-by-step explanation: