What expression is equivalent to (st)(6)?

Adepartment store purchases screen-printed t-shirts at a cost of $5 per shirt. they mark up the price 150% (making the selling price 250% of the store's purchase price) and put them on the sales floor. every month that a t-shirt doesn't sell, the store reduces the selling price by 25%.

Solve each quadratic equation by factoring and using the zero product property. x^2 - 8x + 30 = 3x

With alll of except for the 2 that i did already