The bar graph on the left tells you the amount of CO₂ emitted by a single vehicle of a given type. Liam's family owns both a hybrid and a gasoline car, which means their vehicles emit a total amount of
6,258 + 11,435 = 17,693
pounds of CO₂.
The pie chart on the right says that 51% of CO₂ emissions from a single household comes from operating vehicles. This means that the 17,693 pounds that Liam's family emits is 51% of their total CO₂ emission, so that their total CO₂ emission comes out to
17,693 / 0.51 = 34,692.2
pounds of CO₂.
The pie chart also shows that, in a given household, 18% of CO₂ emissions are due to heating and cooling systems, and 26% due to using appliances. Together, these sources of CO₂ make up 18 + 26 = 44% of total emissions per household.
So, heating/cooling and appliances used by Liam's family emits around
34,692.2 × 0.44 = 15,264.5 ≈ 15,265
pounds of CO₂.