3.show that x=10, Y=4, and Z=7 is a solution to the system below without solving the system formally

Question

x+2y+z=25

4x-y-5z=1

-2x-y+8z=32

Answer 1

Just plug those values of x, y, and z into the equations and see if it's true. I'll do the first one:

x + 2y + z = 25

10 + 2(4) + 7 = 25

10 + 8 + 7 = 25

25 = 25

Yup, true for this one. You try the other two. If you end up with nonsense, such as 14 = 73, then it's not true.