Given Data:
[tex]\begin{gathered} p=-4t+28\ldots(1) \\ p=3t-21\ldots(2) \end{gathered}[/tex]
subsitute equation (1) in equation (2) we gte,
[tex]\begin{gathered} p=3t-21 \\ p-3t=-21 \\ (-4t+28)-3t=-21 \\ -7t+28=-21 \\ -7t=-21-28 \\ -7t=-49 \\ t=\frac{49}{7} \\ t=7\ldots(3) \end{gathered}[/tex]
subsitute t = 7 in equation (1),
[tex]\begin{gathered} p=-4t+28 \\ p=-4(7)+28 \\ p=-28+28 \\ p=0 \end{gathered}[/tex]
Therefore p =0 and t =7
