Given: #1/2k-3=2-3/4k#.
Add #3# to both sides.
#=>1/2k-color(red)cancelcolor(black)3+color(red)cancelcolor(black)3=2-3/4k+3#
#=>1/2k=5-3/4k#
Add #3/4k# from both sides.
#=>1/2k+3/4k=5+color(red)cancelcolor(black)(3/4k)-color(red)cancelcolor(black)(3/4k)#
#=>2/4k+3/4k=5#
#=>5/4k=5#
Multiply by #4/5# on both sides.
#=>(color(red)cancelcolor(black)5)/(color(red)cancelcolor(black)4)k*color(red)cancelcolor(black)4/(color(red)cancelcolor(black)5)=5*4/5#
#=>k=4#