For #1, you are correct to raise both the numerator and the denominator to the 7th power. x^7 cannot be expressed any other way since we do not know the value of x. It is not equal to one unless being raised to the zeroth power. You are right that 2^7=128
but you do not want to then raise 128 to the 7th power. The final expression is x^7/128.
For #2 your final answer is right. Any number raised to the zeroth power is 1. Your process is not correct, however. The result of raising the fraction 4/13 to the zeroth power is 4^0/13^0=1/1=1, not 4^1/13^1.
For #3, you need to raise both the numerator and the denominator to the 8th power. This involves raising a power to a power which requires multiplying exponents. The result is m^72/n^48.