Question 1377
Let x be the width of the stage:
x*(x+10) = 600
(the width times the length whcih is equal to 600)
x^2+10x = 600
x^2+10x-600 = 0
Now factor the equation
(x+30)(x-20) = 0
x = -30 or 20
Because length of anything can not be a negative number, so 20 is the width and x+10 whcih is 30 is the length of the stage.