Tolong dijawab soal mtk ini

a-7 = 6d => 2a -14 = 12d

2(a+4) =  5(d+4) + 9 => 2a + 8 = 5d + 29 => 2a = 5d + 21

2a -14 = 12d
(5d +21) -14 = 12d
5d + 7 = 12d
7d = 7
d = 1

a -7 = 6d
a = 6d + 7 = 13