There is a carbon phase diagram shown in the problem where there is a positive sloped curved line separating the graphite anddiamond region. (Temperature is the x axis and Pressure is on they-axis)
On this line (the equlibrium of graphite and diamond) there isa point "A" that is located on the far right side of the line(3/4 of the way if you move to the right on the line). They ask todetermine whether the enthalpy of point "A" is positive ornegative. The answer is negative but i'm not sure why. So to gofrom graphite to diamond the reaction is endothermic. However, isthe enthalpy negative due to the fact that at some point thepressure and temperature will be so high that the equilibrium needs to shift back to the left (diamond --> graphite) in order tocounteraffect these disturbances and so reaction will be exothermicand thus enthalphy will be negative.