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.
Answer:
24.23
Step-by-step explanation:
The tan(x) would equal to the opposite side over the adjacent one
So 9/20. To get the degree we need to get the arctan of it, so arctan(9/20) = 24.23
This is what I got:
60/50 = X/70
70x60/59 = X
X = 84
Answer:
c
Step-by-step explanation:
come on ! you can literally see that in the chart.
how many parts of the gray 3/8 are covered by the gray 1/4 ?
2 parts = 2/8 are clearly covered by 1/4.
2/8 is what part of 3/8 ?
it is the same question as "2 is what part of 3" ?
is 2 a quarter (1/4) of 3 ? no, 1/4×3 = 3/4 and not 2.
is 2 one third (1/3) of 3 ? no, 1/3 of 3 = 1/3×3 = 1 and not 2.
is 2 two thirds (2/3) of 3 ? ah, 2/3 × 3 = 2. that is correct !
is 2 three quarters (3/4) of 3 ? no, 3/4×3 = 9/4 and not 2.
once you have the same denominator, you can easily compare the numerators and ignore the denominators for such problems.