Answer:
- 10
Step-by-step explanation:
Substitute k = 3, 4, 5, 6 into the expression and sum the terms, that is
-5(3) + 20 - 5(4) + 20 - 5(5) + 20 - 5(6) + 20
= - 15 + 20 - 20 + 20 - 25 + 20 - 30 + 20
= 5 + 0 - 5 - 10
= - 10
