D∩E=D This is because since D is a subset of E then the elements they will have in common are the elements in D and D is not a null set
The answer is 4. I hope this has helped.
Step-by-step explanation:
From the given question it appears that (n-1) is in the numerator's place, if it is so, then let us solve it.

1/4 = 0.25
2/3 = 0.666666667
0.25(0.666666667) = 0.166666667 =

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This is easy just find out what 5^2 equals which will be 5x5=25 (when dealing with a squared number you will always times it by itself. so if you had 10^2 it would be 100.) so now that we know 5^2 is 25 we then can add the 20 which gets 25+20=45! Hope this helps!