jawab no 3 dengan cara jalannya yg tau plisss jawab dan yg gk tau dk usah jawab

jawab
u5 = 17
u8 = 26

u8 -u5 = 26- 17
(8-5)b = 9
3b = 9
b = 3

u5 = 17
a + 4b = 17
a + 12 = 17
a = 5

sn = n/2 ( 2a + (n-1)b)
s20 = 20/2 (2(5) + 19(3))
s20 = 10(10 + 57)
s20 = 670