X-the number
20 · x² = 20 · x |divide both sides by 20
x² = x |subtract x from both sides
x² - x = 0
x(x - 1) = 0 ⇔ x =0 or x - 1 = 0
Answer: x = 0 or x = 1
ANSWER
8 minutes
EXPLANATION
We know that the cost of using the internet in dollars is given by,

Where x is the number of minutes spent on the internet.
In this problem, we have to find how many minutes will 6 dollars buy. In other words, we have to find x for y = 6. To solve the given equation for x, we have to multiply both sides by 4,

And divide both sides by 3,

So, for y = 6, x is,

Hence, $6 will buy 8 minutes.
The number on the left side of the decimal, write it as a large, in this case, three. The number on the right side of the decimal, write as a small number. Then put a ten under the five, and divide the two with a line. A way to remember this is - Imagine you have 3 cookies. The .5 represents a half of a cookie. You need to have all ten parts of the cookie to make a whole cookie. You'd need 5 more pieces of cookie to make 4 cookies. Hope this helps.
19.98. you can round it off to 20 if needed. It would be logical to round it.
3A = M
A + 8 = M - 6
3A = M
A + 8 = 3A - 6
A + 14 = 3A
14 = 2A
A = 7
M = 3A
M = 3 x 7
M = 21
So overall Aaron had 7 shells, and Maria had 21.