Here's one exactly like it that you can use as a guide
to solve yours. I'm just changing your 192 to 40.

x+y+z=40
x=y+z
x=4z

Notice that the first two equations both have (y+z)
I'll put them in parentheses to make it clear:

x+(y+z)=40
x=(y+z)
x=4z

Since the second equation tells us that (y+z)=x, we can
substitute x for (y+z) in the first equation:

x+(x)=40
2x=40
 x=20

Then substitute 20 for x in x=4z

20=4z
 5=z

Finally substitute x=20 and z=5 in x=(y+z)

20=(y+5)
20=y+5
15=y

Now do yours exactly the same way. {Yours will have bigger numbers
because 192 is bigger than 40

Edwin