The unkown side legnth is 9 centimeteres long all you had to do was subtract all the numbers from 44 and what your left with is the unknown side.
You're pretty close. It's all in the details.
A. Correct.
B. Correct.
C. Sign error in the boxed answer. -(-0.5) = 0.5
The graph shows c ≈ 1.855. If a is more than that and decreasing, area is increasing. The sign of dA/dt will be positive. (Compare to D)
D. Units are not shown. Numerical value is correct.
-19.59 is your answer because u do PEMDAS and that would be 8.1*(-1.9) which gives you -15.39 Then you do -4.2+-15.39 and you would get -19.59