hae buddy, yu need tu start with sumthun sumwon mite be abel tu figger...basiks like
????????? maebee yu hav a REKTANGULAR pool ???????????
?????????? maebee flat bottom, so water same depth all over ???????????
?????????? in other werds, yu hav a BOX (WOT guvt krats kall a "rektangular solid" ??????????
Maebee teech want EQUASHUN for volume ???????????
base area=leng*wide=3*(wide+3)*wide
volume=leng*wide*deep=(2*leng-7)*3*wide*(wide+3)
but leng=3*(wide+3), so yu hav [2*3*(wide+3)-7]*3*wide*(wide+3)
or (3*wide^2+9wide)*[6*wide-18 -7]
or 3*wide(wide+3)*(6*wide-25)
or 3*wide*[6wide^2 -7wide-75)