Two moles of an ideal gas with CPCV=53  are mixed with 3 moles of another ideal gas with  CPCV=43. The values of  CPCV for the mixture is

γmixture=n1CP1+n2CP2n1CV1+n2CV2=n1γ1Rγ1−1+n2γ2Rγ2−1n1Rγ1−1+n2Rγ2−1​After rearranging we get, n1+n2γmix−1=n1γ1−1+n2γ2−1​⇒5γmix−1=31/3+22/3 ⇒5γmix−1=9+3=12​⇒γmixure=1+512=1712⇒γmix=1.42