Answer: a = c^(1/2) which is the first answer choice of the list
Work Shown:
a = b^(2/3) ... given equation
a = (c^(3/4))^(2/3) ... replace b with c^(3/4)
a = c^((3/4)*(2/3)) .... multiply exponents
a = c^(1/2) .... Simplify; note the 3's cancel, also 2/4 turns into 1/2
