find x and y

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