Can someone tell me if this is correct?

3958
8
3958
jh
a^2+b^2=c^2
(3958)^2 + (jh)^2 = (8+3959)^2
(3958)^2 + (jh)^2 = 3967^2
15,665,764 + x^2 = 15,737,089
X^2 = 15665764 – 15737089
X^2 = 71325
X = sqrt(71325)
X = 267.06740722..
X = 267.1
the nits are in miles and the final answer is 267.1