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 delta is formed by deposition of sediment at the mouth of a river by water fanning out. 
Fact 2: Erosion is responsible for wearing down exposed places and depositing sediment in level places.

SOLUTION: a delta is formed by erosion.

PROBLEM: Fact 1: an egg requires warmth to survive. 
Fact 2: Heat and warmth help other gift plants.

SOLUTION: an egg requires heat to survive.

PROBLEM: Fact 1: creating paper requires cutting down trees. 
Fact 2: Trees only grow to be cut down.

SOLUTION:
Trees grow for paper to be made.