3 x 10 ^4 as an ordinary number

Compare these two waves: the blue and orange waves have the same pitch, but the blue wave is louder. the blue and orange waves have the same volume, but the blue wave has a higher pitch. the orange wave has a higher pitch, but the blue wave is louder. the blue wave has a higher pitch, but the orange wave is louder.

Pls! does anybody know a shortcut for answering these types of questions in the future?

For each proportion find the unknown number x 1/5/8=×/15