Question

The question's attached in the file; I tried solving it in 4 different ways and ended up confusing myself more and more each time.

Answer 1

(x+3)² = (16+x-3) (x-3)

x²+6x+9=(x+13)(x-3)

x²+6x+9=x²+10x-39

6x-10x=-39-9

-4x=-48

x = 12

=> NM = 12+3 = 15