if y=3x and 4x - 2y=5, then x = ?

y = 3x      (1)

4x - 2y  =  5       (2)

Sub (1)  into (2)   and we have

4x - 2 (3x)  =  5    simplify

4x - 6x   = 5

-2x  =  5        divide both sides by -2

x  =   -5 / 2