a) 2x+3=1 => 2x=1-3 => 2x=-2 => x= -2/2 => x= -1
b) 2x+3= -1 => 2x= -1-3 => x= -4/2 => x= -2
c) 2x+3=7 => 2x=7-3 => x=4/2 => x=2
d) 2x+3= -7 => 2x= -7-3 => x= -10/2 => x= -5
e) 2x+3=21 => 2x=21-3 => x=18/2 => x=9
f) 2x+3= -21 => 2x= -21-3 => x= -24/2 => x= -12