A+2.4=7.8
a=-5.4
5.4+2.4=7.8
The area of D is given by:

The average value of f over D is given by:
Range, if he calculate all of it and checked the price from beginning to end this would be because he found the range
To make a fraction a percent, you have to divide the numerator by the denominator. You get a decimal. Multiply the decimal by 100 to get the percent or just move the decimal two places to the right.
So,
1.
Divide 1 by 5 and you get 0.20
Multiply 0.20 by 100. The answer is 20%
2.
Divide 2 by 3 and you get 0.6666.......
Multiply 0.6666..... by 100 and you get 66.6%
3.
Divide 1 by 40 and you get 0.025.
Multiply 0.025 by 100 and you get 2.5%
4.
Divide 4 by 8 and you get 0.5.
Divide 0.5 by 100 and you get 50%.
5.
Divide 12/16 and you get 0.75.
Multiply 0.75 by 100 and you get 75%.
<em>Hope it helps</em>
Subtract 128.5 from 180 degrees and you get 51.5. Then add 51.5 plus 13, you get 64.5. Subtract 64.5 from 180 and you get 115.5. A triangle's angles all added together equals 180.