3. 15% of 80 is 12 and 16% of 80 is 12.8. Find each percentage of 80 and be prepared to explain your reasoning.

12.08

Step-by-step explanation:

the easiest way to answer this is to set it up in this equation:

15.1/100 = x/80

in this, 15.1 is the percentage over 100 (because 100% is the most you can get) and x is the number that would be 15.1 percent of 80. Cross multiply so that you get 100x = 1208. Divide both sides by 100 to get x by itself. the end result will be x = 12.08

Step-by-step explanation:

Given

In 1990; Income= $39000

In 2010; Income= $70768

Solving (a): An equation in form of f(x) = ax + b

First, we need to determine the slope, a

Taking y as income and x as year index.

When x = 0; y = 39000

When x = 20; y = 70768

Substitute these values in the above formula

Next, is to determine the formula using:

Considering :When x = 0; y = 39000, we have

Make y the subject of formula

Express y as a function of x

Solving (b): Income in 2005

In 2005, x = 15

So:

becomes