x-2y = 1 -----> equation (1)
y²-3xy + 8 = 0 -----> equation (2)
so equation (1) is x = 1 + 2y
now we will put equation (1) in equation (2)
y² - 3xy + 8 = 0
y² - 3 (1+2y) y + 8 = 0
y² - 3y - 6y² + 8 = 0
-5y² - 3y + 8 = 0
5y² + 3y - 8 = 0
(5y+8) (y-1) = 0
5y + 8 = 0
5y = -8
y = -⁸/₅
y-1 = 0
y = 1
so y = -⁸/₅ and y = 1
for y₁
x = 1 + 2y
x = 1 + 2(-⁸/₅)
x = 1 - ¹⁶/₅
x = -¹¹/₅
for y = 1
x = 1 + 2y
x = 1 + 2(1)
x = 1 + 2
x = 3
so (x₁,y₁) = (-¹¹/₅ , -⁸/₅)
and (x₂,y₂) = (3 , 1)