mohon dibantu, plis!

Bab Persamaan Linear
Matematika SMP Kelas VIII

1/(x + y) = a
1/(x - y) = b

a + 2b = 1
a = 1 - 2b

2a - b = 3/4
2(1 - 2b) - b = 3/4
2 - 4b - b = 3/4
-5b = 3/4 - 2
-5b = (3 - 8)/4
-5b = -5/4
b = 1/4

a = 1 - 2b
a = 1 - 2 . 1/4
a = 1 - 1/2
a = 1/2

a = 1/(x + y)
x + y = 1/a
x + y = 1 : 1/2
x + y = 2

jawabannya B