Răspuns:
[tex] {2}^{4} = 2 \times 2 \times 2 \times 2 = 16 \\ {3}^{4} = 3 \times 3 \times 3 \times 3 = 81 \\ [/tex]
[tex] {2}^{4} \times {3}^{4} - 5 \times x = 21 \\ 16 \times 81 = 1296[/tex]
[tex]1296 - 5 \times x = 21 \\ 5 \times x = 1296 - 21 \\ 5 \times x = 1275 \\ x = 1275 \div 5 \\ x = 255[/tex]