Find the value of 5^-3x 2^-1

Solve the equation using the given values: x= -2.5; y= -7.51. 2xy + 2x²

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%.

X+ y = 5 ; x - y =3 solve using linear combination