Use laws of exponents. am/ an = am-n . If you have like bases and you are dividing the expression then to simplify you subtract their exponents. If you were multiplying like bases then you add the exponents.
So 2 is your like base and since were dividing we subtract their exponents. 23/4-1/2 = 21/4. ( I'm assuming you know how to subtract fractions with different denominators). Now you just have to rewrite it as a radical. Your Index is the denominator in the rational exponent and the power of the base 2 is the numerator which happens to be 1. so your answer should be The fourth root of 2.