A= x
B=y'z
N(A union B) = N(A) + N(B) - N(AB)
=2^4 + 2^3 - (2^2)
= 16 + 8 - 4
That is 20...
N(A) we have x in the minimize expression..remaining terms are v,w,y,z each one having two forms( simple and complement) so 2^4 ...
For N(B) same way 2^3 ...
But adding these two some terms are common we need to deduct it..which are 2^2 ...a