The power rule is quite difficult to learn and comprehend at first, however, it gets easier as time goes on!
These answers are:
1. 4x
2. 15x^4+24x^3+3
3. 16x^7+15x^4
The power rule states: b^a derivative is ab^a-1 .. Basically subtract 1 from the exponent and multiply the base b by a.
Any other questions feel free to ask.