Of the 50 parking spots in the garage, 23 are empty. What is the ratio of the number of empty parking spots to the number of full parking spots?

Find the number of full ones by subtracting empty from total:

50 - 23 = 27 full

The ratio of empty to full is written as empty: full

Ratio = 23:27

The answer is 20 days.

After 60 people have joined there will be 460 people in the camp.

The number of days which the provisions will last will be proportional less after the 60 people have joined and will be:-

(400/460) * 23

= (20 / 23) * 23

=  20