#### Answer

Flossing daily and eating red meat more than twice a week will shrink one's life span by $3$ years.

#### Work Step by Step

Flossing daily stretches one's life span by 2 years.
The number represents this is $2$.
Eating red meat more than twice a week shrinks one's life span by 5 years.
The number that represents this is $-5$.
The final effect on one's life span in doing the two can be found by adding the two numbers together:
Effect on one's life span $=2 + (-5) = -3$
Thus, flossing daily and eating red meat more than twice a week will shrink one's life span by $3$ years.