Question 44035
5x-6y=23............(i)
x=6-3y..............(ii)
Substitute equation (ii) into equation (i) for x:
5(6-3y)-6y=23
30-15y-6y=23
7=21y
y=7/21
y=1/3

I hope this helps 
P.S. I am trying to start up my own homework help website. I would be extremely grateful if you would e-mail me some feedback on the help you received to adam.chapman@student.manchester.ac.uk