Viewers of three TV serials in Indore are shown in the diagram. How many viewers watch at most two of the serials?

At most two = everyone except the centre. Total $=24+19+21+6+8+5+7=90$, so at most two $=90-7=83$. 64 counts only exactly one, 19 only exactly two, and 90 includes the 7 who watch all three.