I’m typing fast and don’t have paper so can’t give numbers but I can tell you how to solve. So here we go,
We know that,
6x+15x+75=180 and we also know 3y=15x+75.
Since we know 6x+15x+75=180 we just do 180-75=105
This then means that 6x+15x=105
And that’s as far as I can take you. (This may totally be wrong but if ur really stuck try my way.) (to find answer just put in 15 and 6 until u get it so that you get 105).