Add 60 and 90 to get 150 then divide by 2 and get 75 which is the answer i believe.
There are an infinite amount of equations that pass through a single point. You must provide the slope or y-intercept to get a single equation.
Hope that clarifies.
The answer to this question is:
9x+8/3x^2
60%
40%
The number twenty is double of 10 so think of it as 10 but double the reaction see 10 percent of 20 is .5 but 10% of 10 is one...double .5 hope this helps!