Repetition is a guaranteed way to learn something. If it is a formula you need to learn, try doing flashcards and reading it over and over again until you can spell it without the flahcard. If it is something like factoring, just do a bunch of factoring problems until you get the feel of it.
Answer: 820,000
823,563 rounded to the nearest ten thousand is 820,000
Answer: 3
Step-by-step explanation:
Let E be the event of that student pierces ear and N be the event of that student pierces nose.
Given: 

For any two event A and B, we have

Similarly , 

Hence, 3 students have piercings both on their ears and their noses.
Answer: width= 5cm Length= 7
Step-by-step explanation: