tolong jawab beserta caranya ya. Tolong sekarang

6)
U1 = a = 5
b = 12-5= 7
Un = a + ( n - 1 ) b
U34= 5+ (34-1) 7
= 5 +(33 x 7)
= 5 + 231
= 236. C
7)
antara 100--->300
a = 102 ------>297
b = 3
Un = a + (n -1) b
297= 102+ (n - 1) 3
297= 102+ 3n - 3
297= 99 + 3n
3n= 297 -99
3n= 198
n =198 :3
n = 66
Sn = n/2 ( a + Un)
S66= 66/2 (102 + 297)
= 33 x 399
= 13.167......D