Hi,
The like terms are 2xy, -xy and (1/2)xy, since they have the same variables and powers.
Lets solve the equalities first.
NP>MN
Cancel out the N
P>M
Next
MP<MN
Cancel out the M
P<N
M<P<N
The answer is C.
Plug in (7, 12) for x and y in the equation.
12 = 2(7) + 1
12 = 14 + 1
12 ≠ 15
Therefore, (7, 12) is not on the straight line equation.