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:
Cardiovascular system
Step-by-step explanation:
You can solve this by using the system of equations.
Jan - 4.95 = 2H + 3C
Wayne - 5.45 = 3H + 2C
Use elimination.
-3(2H + 3C = 4.95)
2(3H + 2C = 5.45)
Solve. And you'll get:
-6H + (-9C) = -14.85
6H + 4C = 10.9
Cross out -6H and 6H because they cancel out. And you're left with:
-9C = -14.85
4C = 10.9
Add -9C with 4C, and -14.85 with 10.9.
-5C = -3.95
Divide each side with -5.
C = $0.79
Now to figure out what H is, just substitute the C in one of the equations with 0.79.
5.45 = 3H + 2(0.79)
5.45 = 3H + 1.58
-1.58 -1.58
3.87 = 3H
3.87/3 = 3/3(H)
1.29 = H
Finished!
