3X/ X^(-1)

3x / (x^(-1))

recall some laws of exponents: a number raised to a negative exponent is equal to its reciprocal raised to the positive exponent
for example,
3^(-1) = (1/3)^1 = 1/3
5^(-2) = (1/5)^2 = 1/25

therefore, here, the x^(-1) becomes (1/x)^1 or simply 1/x
3x / (x^(-1))
3x/(1/x)
recall that when we divide, we take the reciprocal of the divisor (the term in the denominator) and the operation becomes multiplication:
3x * (x)
3x^2

hope this helps~ :)