smc

Let the shorter segment be $x$ and the altitude be $y$. The larger segment is then $80-x$. By the Pythagorean Theorem , $$30^2-y^2=x^2(1)$$ and $$(80-x{)}^2=70^2-y^2(2)$$ Adding $(1)$ and $(2)$ and simplifying gives $x=15$. Therefore, the answer is $80-15=\boxed{65}$