Let's name (0.2x+0.7y = 8) as (1) and (4x-25= -0.5y) as (2)
From (1),
0.2x = 8 - 0.7y
x = 5(8- .7y) = 40 - 3.5y ------ (3)
Substitute (3) into (2),
4(40 - 3.5y) - 25 = -0.5y
160 - 14y - 25 = -0.5y
135 = 14y - 0.5y = 13.5y
y = 10 ------(4)
Substitute (4) into (1)
0.2x = 8 - (0.7)(10) = 8 - 7 = 1
x = 1(5) = 5
Therefore x=5 , y=10