tolong bantuin ya ka,buat besok masalahnya,pliss ya ka.. pake cara ya ka.. makasi

jawab

x+ 3y = 9
y =0 , x= 9 --> (9,0)

x + y = 5
x = 0 , y = 5 --> (0,5)

x+ 3y = 9
x + y = 5 .....(-)
2y = 4
y = 2 
x = 3 .....(3, 2)

f(x,y )  = 5x + 7y
f(9,0) = 45
f(0,5) = 35
f(3,2) = 15 + 14= 29
Minimum = 29