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.
X + y = 25
x is the smaller number.
y is the smaller number plus 9 (x + 9).
x + (x + 9) = 25
2x + 9 = 25
2x = 16
x = 8
8 + y = 25
y = 17
The numbers are 8 and 17.
If you mean x * 2, then you simply plug in -3 for x in the function f(-3):
f(x) = x * 2
f(-3) = -3 * 2
f(-3) = -6