Significant Numbers and Scientific Notation Help!

Hello new here and to maths! haha sorry if this is the wrong place I hope it is! So here is the random number equation that I came up with first one is Significant Numbers.

7.6132 x 3.42 = 26.1

This one is Scientific Notation

7.345 x 10^3 ÷ 3.33 10^2 = 2.21 x 10^1

Hope they are right if not can you tell me where you think I went wrong? Also I can write how I worked it out if needed.

In Scientific Notation how do we know what the 10^something will be?

Thanks again!

And if it is the wrong place I am sorry!!!! (Doh)