Answer:
Johnny is wrong.

Step-by-step explanation:
Johnny is wrong.
A better definition would be:
is the set of all elements that belong to at least one A or B.
So, the elements that belong to both A and B, like c and d in this exercise, also belong to
.
So:

Answer is 2 inches per hour.
12 inches/6 hours divided by 6 is 2 inches/ 1 hour.
Answer:
C. 8
Explanation:
One way to solve this is to find 30% of each class, 28 and 24.
30% of 28:
28 • 0.30 = 8.4
30% of 24:
24 • 0.30 = 7.2
You can then find the average of these two numbers.
8.4 + 7.2 = 15.6
15.6 ➗ 2 = 7.8
7.8 rounds up to 8
Another way to solve is to first find the average number of people in each class.
28 + 24 = 52
52 ➗ 2 = 26
You can then find 30% of this number.
26 • 0.30 = 7.8
7.8 rounds up to 8
7+4a=55
4a=55-7
4a=48
a=48/4
a=12