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 greenhouse is used to protect plants by keeping them warm. 
Fact 2: Another well known plant is the Mesquite Bush.

SOLUTION: a greenhouse is used to protect bushes by keeping them warm.

PROBLEM: Fact 1: Cells cannot survive without oxygen. 
Fact 2: Life is responsible for oxygen in the atmosphere.

SOLUTION: cells cannot survive without the atmosphere.

PROBLEM: Fact 1: Osteoporosis is a disease in which osteoclasts are more active than osteoblasts. 
Fact 2: Osteoporosis can also cause a hump in the upper back, often referred to as a dowager's hump.

SOLUTION:
Dowager's hump starts out with osteoclasts being more active than osteoblasts.