1500x=(300+ 1.5x)*( 1500-4x)=450000- 1200x+2250x-6x^2

6x^2+450x-450000=0

x^2+75x-75000=0

x 1=-37.5+((37.5)^2+75000)^0.5=238.9 168

x 1=-37.5-((37.5)^2+75000)^0.5=-3 13.9 168