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.

Fact 1: a calculator is used for adding. 
Fact 2: Calculator performs basic arithmetic, such as addition and subtraction.
arithmetic includes uses for subtraction.

Fact 1: cooking food requires adding heat energy. 
Fact 2: Cooked foods are easier to digest.
Heat energy makes digestion easier.

Fact 1: fire converts chemical energy into light and heat energy. 
Fact 2: Fire is a chemical reaction involving rapid oxidation or burning of a fuel.

A chemical reaction involving rapid oxidation converts chemical energy into light and heat energy.