a) A = ( a - b + c ) - ( b - c - d ) + ( c - d + d )
A = a - b + c - b + c + d + c - d + d
A = a - ( b + b ) + ( c + c + c ) + ( d - d + d )
A = a - 2b + 3c + d
b) B = ( a + b - c ) + ( b + c - a ) - ( a - c )
B = a + b - c + b + c - a - a + c
B = ( a - a - a ) + ( b + b ) - ( c - c - c )
B = -a + 2b + c
c) C = - ( 4a + 5b - c ) - ( 5b + 3c )
C = -4a - 5b + c - 5b - 3c
C = -4a - ( 5b + 5b ) + ( c - 3c )
C = -4a - 10b - 2c
d) D = ( a - 3b + c ) - ( 2a - b + c )
D = a - 3b + c - 2a + b - c
D = ( a - 2a ) - ( 3b - b ) + ( c - c )
D = -a - 2b