Answer:
6 + 4d + 11c
Explanation:
In order to find the perimeter, you add up all the side lengths which would be expressions in this case
(10c + 10) + (c + 5) + (4d - 9)
add like terms: (10c + c) + (10 + 5 - 9) +4d
= 11c + 6 + 4d
which is the same as 6 + 4d + 11c, I just added them in a different order.