so
xyz
x+y+z=12
3x-2y=5
6z+4y=50
so multiply 3x-2y=5 by 2
6x-4y=10
add to 6z+4y=50 and get
6x+6z+4y-4y=10+50
6x+6z=60
distribute
6(x+z)=6(10)
divide both sides by 6
x+z=10
subsitute 10 for x+z in the first equation
10+y=12
y=2
subsitute
3x-2(2)=5
3x-4=5
3x=9
x=3
x+z=10
3+z=10
z=7
x=3
y=2
z=7
number is
327