Okay, the formula for this would be
[tex] a^{2} [/tex] + [tex] b^{2} [/tex] = [tex] c^{2} [/tex]
Lets start with 4.
[tex] 7^{2} [/tex] + [tex] 25^{2} [/tex] = [tex] c^{2} [/tex]
Simplify.
49 + 625 = [tex] c^{2} [/tex]
674 = c
c = [tex] \sqrt{674} [/tex]
c = 25.96
Which is ≈ 26