A store I selling all toaster ovens at 15% off. Write an equation in the form y=kx

This is geometry. could anyone ? i can't fail this class. my grade is quite low already.

Sweet t saved 20 percent of the total cost of the green-eyed fleas new album let there be fleas on earth. if the regular price is $30 how much did sweet save

Astore sells 4 apples for $3 and 3 oranges for $4 if pete buys 12 apples and 12 oranges how much will it cost