Answer:
Step-by-step explanation:
I think the question is card(A)=20,card(B)=15,card(A∩B)=10, then what iscard(A∪B)
You can solve this question by drawing a picture like this to visualize the problem.
Thus the answer is card(A∪B)=card(A)+card(B)−card(A∩B)=25
