1. The problem statement, all variables and given/known data http://puu.sh/1OfE2 [Broken] 2. Relevant equations 3. The attempt at a solution I am not really sure about this one! :( I think it's 1 because http://puu.sh/1OfY0 [Broken] http://puu.sh/1OfYE [Broken] I came up the number by working backwards (assuming the conclusion is true). However, for a proof, I cannot assume the conclusion is true and try proving the hypothesis. Could someone nudge me to the right direction in proving this statement? Thanks!