Diatas ada foto soal tolong jawab ya

No. 6
f(x) = ax + b
f(3) = 15 --> 3a + b = 15
f(5) = 20 --> 5a + b = 20

Kita eliminasi :
3a + b = 15
5a + b = 20
__________ -
-2a = -5
a = 5/2

Kita substitusikan untuk mencari nilai b
3a + b = 15
3(5/2) + b = 15
15/3 + b = 15
b = 15 - 15/3
b = 45/3 - 15/3
b = 30/3
b = 10