Answer:
Step-by-step explanation:
It is often easiest to use "military time". That is, add 12 to all the afternoon numbers and do the subtraction in the usual way. Of course, 1 hour = 60 minutes, so 10 minutes = 10/60 hour = 1/6 hour.
Mon: 15:10 -8:00 = 7:10 = 7 1/6
Tue: 15:25 -8:05 = 7:20 = 7 1/3
Wed: 14:30 -8:00 = 6:30 = 6 1/2
Thur: 14:45 -7:55 = 7:(-10) = 6:50 = 6 5/6
Fri: 15:38 -7:58 = 8:(-20) = 7:40 = 7 2/3
_____
Some calculators have nice features for working with degrees, minutes, and seconds. In this context, degrees and hours are the same thing. That is, the base-60 arithmetic is the same whether you consider the numbers to be hours or degrees. Similarly, some calculators convert nicely between decimal fractions and mixed numbers. In short, a suitable calculator will almost do this math for you. (You just need to add 12 to all the numbers in the column on the right.)
Answer:
im pretty sure the ones that say "if not replaced" are independant, sorry if im wrong but im trying to help you out :)
Step-by-step explanation:
The letter x is a placeholder for a number. If we knew what x was, then we can replace it with that number. For now it's unknown.
We start off with x markers in a single box. Then 15 are given out to be left with x-15 markers. This happens exactly 3 times which is what the diagram shows
3 copies of (x-15) = 3*(x-15) = 3x- 45
Put another way, we have 3 'x's that add to 3x, and we have 3 copies of "-15" which combine to -45
So,
3x-45 = 90
3x-45+45 = 90+45 ... add 45 to both sides
3x = 135
3x/3 = 135/3 .... divide both sides by 3
x = 45
Therefore, we started off with 45 markers in each box. If we take 15 away then x-15 = 45 - 15 = 30 markers are left. Then triple this to get 3*30 = 90 which is the total amount left over. This helps confirm the answer.
Final Answer: 45 markers were originally in each box
