A constant-volume gas thermometer reads 70.0 kPa at the triple point of water, 273.16 K.

Ideal gas: $pV = nRT = Nk_BT$, with $R = 8.31\ \text{J mol}^{-1}\text{K}^{-1}$, $k_B = 1.38 \times 10^{-23}\ \text{J/K}$, $N_A = 6.02 \times 10^{23}\ \text{mol}^{-1}$. For a fixed amount, $\dfrac{p_1V_1}{T_1} = \dfrac{p_2V_2}{T_2}$. Always use kelvin. A constant-volume gas thermometer reads $T = 273.16\ \text{K} \times \dfrac{p}{p_{\text{tp}}}$.