Question

A concert orchestra plays a concert at your school, producing a sound intensity of 90 dB. At a point in the performance, a soloist takes over and plays with a sound intensity of 70 dB. How many times more intense is the entire orchestra than the soloist?

Answer 1

All eardrums are moved by sound pressure deviations in pascals and not by intensity.
We measure the sound with an SPL meter. SPL = Sound Pressure Level.
Sound pressure is a sound field quantity. Sound intensity is a sound energy quantity.

Answer 2

The full orchestra produces sound that is 20 dB more intense than the soloist alone produces.

20 dB is 10^2.0 = 100 times as much sound power