Answer
$$0.225$$
Work Step by Step
Using the rules of logarithms, we find:
$$\ln \left(1.7\cdot \:2.1^{3x}\right)=\ln \left(2\cdot \:4.5^x\right) \\ \ln \left(1.7\right)+3x\ln \left(2.1\right)=\ln \left(2\right)+x\ln \left(4.5\right) \\ x=\frac{\ln \left(\frac{2}{1.7}\right)}{\ln \left(\frac{9.261}{4.5}\right)} \\ x=0.225$$
