soal no 2 saya nga paham

Diket=
jumlah garis sejajar L 1 = 17+11
jumlah garis sejajar L 2 = 11+7
t 1 = t 2 = 7
Ditanya =
luas seluruh = ?
Jawab =
L 1 = 1/2 x jumlah garis sejajar x t
= 1/2 x (17+11) x 7
= 1/2 x 28 x 7
= 14 x 7
= 98
L 2 = 1/2 x jumlah garis sejajar x t
= 1/2 x (11+7) x 7
= 1/2 x 18 x 7
= 9 x 7
= 63
L 1 + L 2 = 98+63
= 161