Question 10869: How do you solve this: 3 5/6 -7 1/2. I tried using 12 as the lcd and still now coming up with the right answer. We're doing signed numbers right now and it is confusing me a lot ...is there a simple rule to remember
Answer by longjonsilver(2297)   (Show Source):
You can put this solution on YOUR website! the strictly correct version of this is as follows:
3 and 5/6 is 23/6 in total (since the 3 is 18/6)
7 and 1/2 is 15/2 in total (since the 7 is 14/2)
so we have 23/6 - 15/2, which we cannot do, since the 2 denominators are different. We need them to be the same number: 12 would do fine, but why not choose 6? This is far less work :-)
15/2 --> 45/6
So, now we have 23/6 - 45/6
which is -22/6
which is -3 and 4/6
or, better, -3 and 2/3
jon.
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