Stupid Athena! (who will kill me once she reads the title)

I know only a little, don't ask me about calculus! $y=3\sin(x)=4\cos(x)$ $\dfrac{\text{d}y}{\text{d}x} = \dfrac{\text{d}(3\sin(x))}{\text{d}x}-\dfrac{\text{d}(4\cos(x))}{\text{d}x} \text{ (Sum rule)}$ $\dfrac{\text{d}y}{\text{d}x} = 3\cos(x) - 4(-\sin(x)) \text{ (Derivative of}\sin(x) \text{ is} \cos(x) \text{ and that of }\cos(x) \text{ is } -\sin(x))$ $\boxed{\dfrac{\text{d}y}{\text{d}x} = 3\cos(x) + 4\sin(x)}$

Guys! Now Athena is asking me how I solved it (basically how I cheated and asked you), so please post solutions fast!!!!