when you want to clear a bit you use AND, set a bit OR

portc: x11111

PORTC=PORTC | %00011111

<hr>
porta: xxxx10x,

for this one you may also do it simple..
TempVar=PORTA
TempVar.1=0
TempVar.2=1
PORTA=TempVar

OR, in some case, the following will work without much problem
PORTA.1=0
PORTA.2=1

HTH