Answer:
a. or 
Step-by-step explanation:
Slope is equal to y1-y2 over x1-x2.
So the equation would be:

2-(-1)=2+1=3
-3-(-1)=-3+1=-2
So the answer is:

Xm=(2+2)/2=2
Ym=(1+4)/2=2.5
(2,2.5)
-1584.
multiply 42 times 42 the subtract that from 180
Answer:
let remaining angle in heptagon be a.
a+64=180(linear pair)
a=116
again
x+155+90+163+a+121°=720(sum of interior angle of hexagon is (6-2)×180°)
x+529+a=720
x+116=720-529
x=191-116=75