a,[(-17)-13]+(-20)
=-30-20
=-50
b,777-(-133)-60-50
=910-110
=800
c,-(-319)+(-127)-312+20
=192-292
=-100
a) [(-17)-13]+(-20)
=[(-17)+(-13)]+(-20)
=-30+(-20)
= -50
b)777-(-133)-60-50
=777+133-60-50
=910-60-50
=850-50
=800
c)-(-319)+(-127)-312+20
=319+(-127)-312+20
=192-312+20
=-120+20
=-100