i need help with number 10, i don’t understand it

Answer:
[tex]6x^2+10x-24[/tex]
Step-by-step explanation:
[tex]\text{Solution: }\\\\\text{The formula for the area of rectangle with width }(w)\text{ and length}(l)\text{ is:}\\\text{Area of rectangle = }l\times w\\\\\text{In this case, length}(l)=6x-8\text{ and width}(w)=x+3.\\\\\therefore\ \text{Area of rectangle = }(6x-8)(x+3)=6x(x+3)-8(x+3)\\\text{or, Area of rectangle = }6x^2+18x-8x-24\\\text{or, Area of rectangle = }6x^2+10x-24\\\\\text{This is the required polynomial.}[/tex]