tolong ya segera dijawab:)))

y + z = 10 ....(1)
3x - 4y = 0 ....(2)
x + 2z = 18 ....(3)

z = 10 - y ....(4)

x + 2(10 - y) = 18
x + 20 - 2y = 18
x - 2y = -2 ....(5)

eliminasi pers (2) dan (5)

3x - 4y = 0 |x1| 3x - 4y = 0
x - 2y = -2 |x3| 3x - 6y = -6

2y = 6
y = 3

x - 2y = -2
x - 2(3) = -2
x - 6 = -2
x = 4

z = 10 - y
z = 10 - 3
z = 7

maka,
a + b + c = 4 + 3 + 7 = 14

jawabannya (A)