Q:

Prove the following statement.

could someone check to see if i have a correct proof. Thank you.
If $m+n > 50$, then $m > 25$ or $n >25$ (use proof by contradiction)
So far i have:
By contradiction. If m + n > 50 and m and n are less than or equal to 25.
let m = 25 and n = 25. By definition m + n > 50. But m(25) + n(25)= 50, So this is contradiction. Hence the statement is true.  

A:

You only proved it for a specific case, you need to prove it in general. 
Assume $m+n>50$ and $m\leq 25$ and $n\leq 25$. Then $m+n\leq50$, a contradiction.

