David has two younger sisters, jane and sally. jane is 2 years older than sally and david is 4 times older than jane. sally is z years old. part a write two equivalent expressions that represent david’s age in terms of sally’s age, z, and explain how the two expressions relate to one another. part b which expression is more useful? why?

Part A:

Given that Sally is z years old and Jane is 2 years older than Sally, then Janes age is given by z + 2.

Given that David is 4 times older than Jane, then Davids age is given by 4(z + 2)

Therefore, two equivalent expressions that represent David’s age in terms of Sally’s age, z are 4(z + 2) and 4z + 8.

Part B:

The expression that is more useful is 4z + 8 because it is in a simplified form and given the direct relationship between David's age and Sally's age.