Slope = change in y / change in x
Use the two pints shown on the graph.
Slope = ( 0- -2) / ( -6 -2)
Slope = 2/-8
Slope = -1/4
answer: slope = -1/4
We know that
applying the law of cosines
c²=a²+b²-2*a*b*cos C
in this problem
a=10 m
b=11 m
c=13 m
C=?
c²=a²+b²-2*a*b*cos C----> cos C=[a²+b²-c²]/[2*a*b]
cos C=[10²+11²-13²]/[2*10*11]----> cos C=0.2364
C=arc cos (0.2364)----> C=76.33°
the answer is
76.3°