5x+2y=-3 dan 7x+8y=1 nilai x-y adalah A. -2 B.-1 C. 0 D. 1

5x + 2y = -3.....(pers.1)
7x + 8y = 1......(pers.2)

Elimimasi pers.1 dan 2
20x + 8y = -12.......(pers.1 dikali 4)
7x + 8y = 1...............(pers.2)
__________ _
13x = -13
x = -13/13
x = -1

Substitusi x = -1 ke pers.1 atau 2
7x + 8y = 1
7 (-1) + 8y = 1
-7 + 8y = 1
8y = 1 + 7
8y = 8
y = 8/8
y = 1

Nilai x - y
= x - y
= -1 - 1
= -2 (Opsi A)