The answer is -1
The expression is 14a - 72r - c - 34d. Let's rewrite it:
14a + (-72r) + (-c) + (-34d)
The coefficient of a term is the value beside the term.
For example, the coefficient of 5x term is 5.
For the a-term (14a) of our expression, the coefficient is 14.
The coefficient of the c-term (-c) will, therefore, be -1:
-c = -1c
