Convert 2.3 10^-4 and 4.6 10^-5 into decimals, obtain your solution; and finally, convert that number into scientific notation.
2.3 (10^-4) = .00023
6 10^-5 = .00006
.00023 - .00006 = .00017
and finally, .00017 = 1.7 10^-4
Your answer is 1.710^-4
Hope this helps!