The way the angles are labeled tell you that they are all congruent. The two triangles you see here also share the side that joins them. Then by the angle-side-angle postulate, the two triangles are congruent, so x + 23 = 13, or x = -10.
3 1/4 times 4 is 16 then time 5 1/2 =71.5
I'll help you out with 3 questions.
For #1, you kind of figured it out yourself
That 90 degree angle on paper means that m/1 and m/2 make up 90
If m1 is 50, then just subtract m1 (50) from 90, making it 40. m/2 is 40
If Angle M4 is 45 degrees then angle M3 is 180-45 since they both make up a 180 degree angle.
There are 180 degrees in a triangle
If m 8 = 78
and m 9 = 60
m 10 is 180 - 78 - 60
The mean would be 58!! Basically what you’re doing to get the mean is adding all of the numbers together and dividing by how many you’re adding. In this case, you would add all of the numbers and divide by 8 because you have 8 numbers ! :D
Isolating the variable terms and dividing by 4, we have 
Taking the square root, we have 
