The expression 0.09x+(x−30) models the final price of a bicycle with an instant rebate in a state that charges a sales tax. enter the amount of money of the instant rebate in the box.

I believe that the amount of the instant rebate is $30.  X represents the price of the bike, 0.09 is the sales tax. 

So if the bike cost $100:
0.09(100) + (100-30) = 9 + 70 = $79

Although I think I would want them to tax the bike after the instant rebate and not on the original price. 

If I'm wrong about the instant rebate then it would be 1.09x-30.  Hope this helps.

Yo no me sé esa mala mia