tolong dijawab ya!!!

Un = a + (n-1)b

U5 = a + 4b = 30
U10 = a + 9b = 50

Eliminasi
a + 4b = 30
a + 9b = 50
----------------- -
-5b = -20
b = 4

Subtitusi
a + 4b = 30
a + 4.4 = 30
a + 16 = 30
a = 14

U7 = a + 6b
= 14 + 6.4
= 14 + 24
= 38