1. X+7=21
-7 -7
X=14
2. X-5=13
+5 +5
X=18
3. 4x=48
— —
4 4
X=12
4. 7(X/7)=(15)7
X=105
I think the answer might be 280
Total number of ways to make a pair:
The first player can be any one of 7 . For each of those . . .
The opponent can be any one of the remaining 6 .
Total ways to make a pair = 7 x 6 = 42 ways .
BUT ... every pair can be made in two ways ... A vs B or B vs A .
So 42 'ways' make only (42/2) = 21 different pairs.
If every pair plays 2 matches, then (21 x 2) = <em><u>42 total matches</u></em> will be played.
Now, is that an elegant solution or what !
