1 4 S = 3 t 4 {\displaystyle {\frac {1}{4}}S={\frac {3t}{4}}}
t 4 + 3 t 8 + t 8 = t − 1 2 t + 3 t + t = 8 t − 8 6 t = 8 t − 8 2 t = 8 t = 4 ↓ S = 3 ∗ 4 = 12 {\displaystyle {\begin{aligned}&{\frac {t}{4}}+{\frac {3t}{8}}+{\frac {t}{8}}=t-1\\&2t+3t+t=8t-8\\&6t=8t-8\\&2t=8\\&t=4\\&\downarrow \\&S=3*4=12\\\end{aligned}}}