First find out the selling price of the clarinet, this is:
Discounted price / ( 1 - discount rate)
[tex]\frac{93.60}{(1-20\%)}=\frac{93.60}{(1-0.20)}=\frac{93.60}{0.80}=117[/tex]
This selling price is 30% more than what the store paid so the price the store paid was:
[tex]\frac{117}{1+0.30}=\frac{117}{1.30}=90[/tex]
Answer: the store pay for the clarinet $90
