Abcd is a parallelogram.find the measure of abc

Step-by-step explanation:

First you need to find the mean of the set so 10+12+8+2=32/4=8

Mean=8

Then subtract the mean of each number and square the result

10-8=2^2=4

12-8=4^2=16

8-8=0^2=0

2-8=-6^2=36

new data set: 0,4,16,36

Next find the mean of this set of data

0+4+16+36=56/4=14 now take the square root of that mean

sqrt14=3.74

Hope this helps