tolong pake caranya, cepat ya

[tex]k \: = 2 \times (p + l) \\ 80 = 2p + 2l \\ 80 = 2p + 2(12) \\ 80 = 2p + \: 24 \\ 80 - 24 = 2p \\ 56 = 2p \\ p = 56 \div 2 \\ p = 28[/tex]