\(\left(4-a\right)-\left(2a-11\right)-4=5\)
\(4-a-2a+11-4=5\)
\(11-3a=5\)
\(-3a=5-11\)
\(-3a=-6\)
\(3a=6\)
\(a=6:3\)
\(a=2\)
\(\left(11-a\right)-\left(a-2\right)-21=5\)
\(11-a-a+2-21=5\)
\(-8-2a=5\)
\(-2a=5+8\)
\(-2a=13\)
\(a=-13:2\)
\(a=-6,5\)