The answer is in the photo. Hope this helps
It's true because a pint is used to locate co-ordinates and has no size or dimension
Very easy:
Common denominator:
-5/10w - 3/5 = 2/10w
- 3/5 = 7/10w
-30 = 35w
-30/35 = w
-6/7 = w
That's how you do it mate ;)
1/2 + 3/18 = 9/18 + 3/18 = 12/18 = 2/3
3/45 + 6/50 = 1/15 + 3/25 = 5/75 + 9/75 = 14/75
You can find a common denominator using the two denominators multiples.