(20+x) x (30+x)-600=1000

600+20x+30x+x^2-600=1000

the 600's cancel out

20x+30x+x^2=1000

50x+x^2=1000

50x/50+x^2=1000/50

x^2=20

sqrt x^2=sqrt 20

x=4.4721

x=4.5(approx)

600+20x+30x+x^2-600=1000

the 600's cancel out

20x+30x+x^2=1000

50x+x^2=1000

50x/50+x^2=1000/50

x^2=20

sqrt x^2=sqrt 20

x=4.4721

x=4.5(approx)