TASK DEFINITION: Combine the given two facts to write a concluding fact. Note that there should be some parts of the first and second facts that are not mentioned in this conclusion fact. Your combined fact should be the result of a chain between the two facts. Chains form when two facts connect together to produce a concluding fact. An example of a chain is: "pesticides cause pollution" (fact1) + "pollution can harm animals" (fact2) → "pesticides can harm animals" (conclusion fact). Parts of the concluding fact overlap with the first and the second fact. To construct such a  concluding fact, a useful way is to borrow the subject from one fact and the ending conclusions from another fact.
PROBLEM: Fact 1: a vehicle is used for transportation. 
Fact 2: Cars are vehicles and trucks are vehicles.

SOLUTION: A car is used for transportation.

PROBLEM: Fact 1: rocks interacting with wind over long periods of time causes weathering. 
Fact 2: Rock weathering and erosion produces a continuous stream of sediments that are laid down in layers.

SOLUTION: rocks interacting with wind produces sediments.

PROBLEM: Fact 1: boulders are formed by glaciers melting sometimes. 
Fact 2: Glaciers are truly rivers of ice.

SOLUTION:
Boulders are formed by bodies of ice.