Me i don't understand : it's due tomorrow : meee :

I think what you have to do is add up A B and C so you know how much space they take out of the 456 cm which is the length of the wall. Then you subtract 456cm (which is the total) *the length of the wall* by the result you got from the addition. And then the result you get divide it by 2 so it would give you what is the width of D and E since it says they're equal.
But the equation Idk.. still got me thinking

Hope that helps.. :)

For part one, round the number of seconds in a year, to an easy number, depending on how many significant figure then divide that by 3600, the number of seconds in an hour to get the number of hours in a year. for part 2 do the same but use the exact number instead of the rounded, scientific notation is expressed by using a number between 1 and 10 multiplied by a power of 10 which is how many digits to the left (positive exponent) or right (negative exponent) you must move to get a number from 1 to 10
for part three just explain what is the same or different about your 2 answers.