A partial solution to the equation [ax+b]=cx+d

line 1 [ax+b]= cx+d

line 2 -ax-b= cx+d

line 3 (-a-c)x= d+b

line 4 x= d+b/-a-c for  x less than or equal to -b/a

the first error recorded is a. 1

b. 2

c. 3

d. 4