X – y +z = 5
x + y + 2z = 19
x + y + z = 15

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

51

step-by-step explanation:

73-22=51 the   mass number minus the amount of protons gives you the amount of neutrons