Multiply first equation by 2:
10x + 2y = 18
Subtract the second equation from this so that the 2y terms cancel:
10x - 3x = 18 - 4
7x = 14
x = 2
Plug into first equation to find y:
5(2) + y = 9
10 + y = 9
y = -1
The answer is (2,-1)
I’m guessing you meant central tendency.
I’d say the mean is the best measure for period 2. This is because it doesn’t have any extremely low or high values which could distort the mean value.
If it did ie. 8, then I would choose median as it is less affected by anomalous results
The answer is 8/32 because 8 x 4 = 32
5x - 15 = 2x - 6
3x = 9
x = 3
Y = 5(3) - 15
Y = 0
(3,0)