20+2N=52
now subtract 20 from each side, to get 2N alone
2N=32
now divide each side by 2
N=16
With the curve

parameterized by

with

, and given the vector field

the work done by

on a particle moving on along

is given by the line integral

where

The integral is then


Mark and Don have to sell 11 and 59 marbles respectively.
<em><u>Explanation</u></em>
Lets assume, the number of marbles Mark has is 
As, Don has 4 more than 5 times the number of marbles mark has, so the number of marbles Don has 
Question says that the total number of marbles is 70. So, the equation will be...

<em>So, the number of marbles Mark has = 11 </em>
<em>and the number of marbles Don has =
</em>
37 + x = 2(14 + x)
Explanation:


subtract both sides by 28
9 + x = 2x
subtract both sides by x
9 = x