Increasing order of acid strength among p-ethoxyphenol, p-methylphenol, and p-nitrophenol is 

In p-nitrophenol, the p-nitrophenol is extremely stable due to conjugation between negative charge of oxygen atom, ring and -NO₂ group. So, it is mostly acidic.

In p-methoxyphenol, the conjugate base is extremely destabilized due to +R effect of -OCH₃ group.

In case of p-methyl phenol, it's conjugate base is comparatively a little bit more stable than that of p-methoxy phenol.

Thus, the increasing order of acidic strength is: 

P-Nitrophenol>p-Methyl phenol>p-Methoxyphenol