Revise the following sentences to make one of the existing sentences subordinate to the other.

People know they are going to have to retire; they often do not save enough money to do so comfortably. (this one is my answer, but I like the second one better)

People know they are going to retire, and often do not save enough money to do so comfortably

I would use the second one; however I would use 'but' in place of 'and'

Neither sentence has one of the clauses subordinate to the other.

Start with "Although" followed by the second clause; then use the first clause as the independent clause.

What do you get?

To make one of the existing sentences subordinate to the other, you can use a subordinating conjunction such as "because" or "although". Here's a revised sentence using "because" to subordinate the second sentence to the first:

Because people often do not save enough money to retire comfortably, they know they are going to have to retire.

This revision maintains the same meaning as the original sentences but presents the cause-effect relationship between the two ideas more clearly.