An algebra problem by Yujie Cai

given that , x=2

so, y=2kx

or, y= 4k......................................(1)

again, y=5kx/2 -3

or,y= 10k-6/2...............................(y)

now,    10k-6/2  =  4k


 or,   2k   =24

or, k= 12

Substitute $kx = z$

$2z + 9 = (5/2)z - 3$

$12 = (1/2)z$

$z = 24$

$kx = 24$ , so if $x = 2$ , $k = 24/2 = 12$

Substitute for x

Solve it by comparison

Isolate for k