Almost a billion people on the planet don't have access to clean drinking water." if there were 7.2×109 people in the world in 2014, then approximately what percent of them lived without clean drinking water? round to the nearest tenth of a percent.

13.9%.

7.2 x 10^9 = 7,200,000,000.

Since 1 billion = 1,000,000,000 out of these 7,200,000,000 do not have access to clean water, we find the percent by taking:
1,000,000,000/7,200,000,000 = 10/72 = 13.9%