a) a + b + c + d = 2347 + 2003 + 792 + 27 = 5169
b) a + b - c - d = 2347 + 2003 - 792 - 27 = 3531
c) b - c + d = 2003 - 792 + 27 = 1238
d) a - d - c + b = 2347 - 27 - 792 + 2003 = 3531
e) ( a + b ) - ( c + d ) = (2347 + 2003) - (792 + 27) = 4350 - 819 = 3531
f) ( b + c + d ) - a = (2003 + 792 + 27) - 2347 = 2822 - 2347 = 475