Let n = total boxes (5)
Probability (p) = 1 out of 4 = 1/4 = 0.25
Probability she wins at most 1 out of 5 is p(x <=1) Which is also = p (x =0) + p(x=1)
Probability of not winning would be 0.75 ( 1-0.25)
No prizes in 5 boxes = 0.75^5
1 prize in 5 boxes = 5 x 0.25 x 0.75^4
Total probability = 0.75^5 + 5 x 0.25 x 0.75^4 = 0.63