Countable equations: x+y+z = 35, (1) 2x-5 = y, (2) 1/3y = 1/2z (3).

(2) It can be transformed into: x=(5+y)/2(4)

(3) It can be transformed into: z=2/3y(5)

Bring (4) and (5) into (1) to get: y= 15.

Bring y= 15 into (4) to get x= 10.

Bring y= 15 into (5) to get z= 10.

So x= 10, y= 15 and z= 10.