X·【1000-20·(X-25)】=27000
X·【1000-20X+500)】=27000
X·【1500-20X】=27000
1500X-20X^2=27000
X^2-75X+1350=0
(X-45)(X-30)=0
X=45或X=30
X·【1000-20·(X-25)】=27000
X·【1000-20X+500)】=27000
X·【1500-20X】=27000
1500X-20X^2=27000
X^2-75X+1350=0
(X-45)(X-30)=0
X=45或X=30