\[\boxed{\text{5.536.}}\]
\[1)\ (3x + 5x) \cdot 45 = 1080\]
\[8x \cdot 45 = 1080\]
\[8x = 1080\ :45\]
\[8x = 24\]
\[x = 24\ :8\]
\[x = 3.\]
\[2)\ (9x - 4x) \cdot 72 = 1080\]
\[5x = 1080\ :72\]
\[5x = 15\]
\[x = 15\ :5\]
\[x = 3.\]
\[3)\ (10z - 4z)\ :4 = 12\]
\[6z = 12 \cdot 4\]
\[6z = 48\]
\[z = 48\ :6\]
\[z = 8.\]
\[4)\ (8z + 10z)\ :9 = 16\]
\[18z = 16 \cdot 9\]
\[18z = 144\]
\[z = 144\ :18\]
\[z = 8.\]