I assume
has counterclockwise orientation when viewed from above.
By Stokes' theorem,

so we first compute the curl:


Then parameterize
by

where the
-component is obtained from

with
and
.
Take the normal vector to
to be

Then the line integral is equal in value to the surface integral,



The number is = 10x+y
if reverse the digits, the number is: 10y+x
The sum fo its digits is = x+y=5
I suggest this system of equations:
(10y+x)-(10x+y)=27 ⇒9y-9x=27
x+y=5
We can solve this system of equations by equaliztion method
x=5-y
9y-9(5-y)=27
9y-45+9y=27
18y=27+45
18y=72
y=72/18
y=4
x=5-y
x=5-4=1
The number is: 10x+y=10(1)+4=14
Answer: the number is 14
It would be -(-31) because a negative and negative is a positive
The given system of equation that is
and
has infinite number of solutions.
Option -C.
<u>Solution:</u>
Need to determine number of solution given system of equation has.

Let us first bring the equation in standard form for comparison


To check how many solutions are there for system of equations
, we need to compare ratios of 
In our case,



As
, so given system of equations have infinite number of solutions.
Hence, we can conclude that system has infinite number of solutions.