A balloon carries a total load of 185kg at normal pressure and...

${ρ}_{air} = gv = mg$

${ρ}_{air} = V = 185kg$

${ρ}_{air}gv = m ' g$

${ρ}_{air}\left(\dfrac{{P}^{'}}{P} \times \dfrac{T}{{T}^{'}}\right)V = {m}^{'}$

$185\left[\dfrac{45}{76} \times \dfrac{300}{266}\right] = {m}^{'}$

$m ’ = 123 . 54kg$