Answer:
x=5,y=5,z=5
Step-by-step explanation:
x=15-y-z
15-y-z-y+z=5
15-2y=5
y=5
x+y+z=15
15-2y+y+z=15
15-10+5+z=15
z=5
x-y+z=5
x-5+5=5
x=5
