Solve this equation with substitution method : -

x+5 = 3 (y+5)

x-5 = 7 (y-5)

From the first equation,

x+5 = 3 (y+5)

x = 3y + 15 - 5

Now substitue x in the second equation with (3y + 15 - 5).

x-5 = 7 (y-5)

(3y+15-5) - 5 = 7 (y-5)

3y + 5 = 7y - 35

-4y = - 40

y = 10

Since y is 10, and x is (3y + 15 - 5),

x = 30 + 15 - 5 = 40