4. Lucy is k years old. She has a sister who is three years younger than she is and another sister who is five years less than twice Lucy's age. Write an expression, in
simplified form, for the sum of the three girls' ages.

4k - 8

Step-by-step explanation:

Lucy is k years old so we know k is an important part of this problem.
Sister 1 is 3 years younger, so she is k - 3 years old.
Sister 2 is 5 years less than twice Lucy's age therefore, she is 2k (twice Lucy's age) - 5 years old.
Now we have: k + (k - 3) + (2k - 5)
We can simplify like terms with the k's and get 4k. then we add (-3) and (-5) to get 4k - 8.

Hope this helps!