The total volume of the jar is (in cubic inches):
[tex]V=8x^2+2x-4[/tex]Josh pours inside the jar a volume of water (in cubic inches):
[tex]V_0=4x^2-3x+2[/tex]After Josh pours inside the jar a volume of water V0 (in cubic inches), the jar will still hold a volume equal to the difference between the total volume V and the volume of water poured V0:
[tex]\begin{gathered} V^{\prime}=V-V_0 \\ V^{\prime}=(8x^2+2x-4)-(4x^2-3x+2) \\ V^{\prime}=8x^2-4x^2+2x+3x-4-2 \\ V^{\prime}=4x^2+5x-6 \end{gathered}[/tex]Answer: 4x² + 5x - 6