4x=12. Divide by 4 so x=3
B is the correct answer.
We are adding the border of x thickness to all 4 sides of the table. This makes the new width of the table 36+x+x = 36+2x and the new length of the table 72+x+x=72+2x. To find the area, we multiply the length and width:
(36+2x)(72+2x) = 3006
Multiplying the binomials, we get:
36*72 + 36*2x + 2x*72 + 2x*2x = 3006
2592 + 72x + 144x + 4x² = 3006
Combining like terms gets us
2592 + 216x + 4x² = 3006
Subtract 3006 from both sides:
2592 + 216x + 4x² - 3006 = 3006 - 3006
-414 + 216x + 4x² = 0
Writing in standard form we have
4x²+216x-414=0
(3n-2) x (4n+1) =0
All you need to do is to find what value of n makes each factor equal 0.
First Term:
3n-2 = 0
3n = 2
n = 2/3
Second Term:
4n+1 = 0
4n = -1
n = -1/4
n ={2/3, -1/4}
He took home $160 after donating 20% (which is $40)
