50% to 36.75 what is the original price

Cynthia takes her dog to the park every 2 days. she bathes her dog every 7 days. if she took her dog to the park and bathed him today, how long will it be until she does both on the same day again?

Which expressions are equivalent to k/2 choose 2 answers: a k-2 b 2/k c 1/2k d k/2 e k+k

Can someone check if i did this correct. it’s number 4 if you’re wondering.