\(a,524-\left[\left(476+524\right)-76\right]\)
\(=524-1000+76\)
\(=600-1000\)
\(=-400\)
\(b,\left(67-5759\right)+5759\)
\(=67-5759+5759\)
\(=67\)
\(c,4.\left(2020+2019\right)+4.\left(-2019\right)\)
\(=4.\left(2020+2019-2019\right)\)
\(=4.2020\)
\(=8080\)