For the process shown in volume-temperature (V – T ) diagram the pressure from a to b  

The given V - T graph has a mathematical equation V = V_o + mT,

Here m is the +Ve slope  and V₀ is the y intercept which is also +Ve.

Substituting the value of V in ideal gas equation P(V₀ + mT) = RT

$\mathrm{P}=\frac{\mathrm{RT}}{\left({\mathrm{V}}_0+\mathrm{mT}\right)}=\frac{\mathrm{R}}{{\displaystyle \frac{{\mathrm{V}}_0}{\mathrm{T}}}+\mathrm{m}}$

So as T increases, P increases.