Set it up in a proportion.
8 (oil)/5 (salad dressing) = x/7
cross multiply to get 11.2
7=x^2+20x+82
0=x^2+20x+75
What adds to 20 and multiplies to 75? 5 and 15.
x^2+5x+15x+75
x(x+5) 15(x+5)
(x+15) (x+5)
Zeroes are x= -5 and x= -15
I feel it should be 30 because x represents the number of lessons, and 30 is multiplied by that.
A. $90
150 x .40= 60
150-60=90
