Simplifying the given expression we get,B=I−C15adj(A)+C25(adj(A))2−C35(adj(A))3+C45(adj(A))4−C55(adj(A))5
⇒B=(I−adj(A))5
Now, A=[20−12]⇒adj(A)=[2012]
So,B=[−10−1−1]5
⇒−B=[1011]5=[1051]
⇒B=[−10−5−1]
Now, sum of elements of matrix B =−1−5−1=−7