It may be easier to approach this problem in 2 steps: 1) multiply together 2.3 and 1.5, obtaining 3.45. 2) mult. together 10 and 10^(-2), obtaining 10^(-1).
Then write the final answer as 3.45*10^(-1).
Given that 2.3 and 1.5 are accurate to only one decimal point, it's more appropriate to round off 3.45, to obtain 3.5. Then the final answer is
3.5*10^(-1).