we have
4x + y + 5z = 5 -------> equation A
8x + 2y + 10z = 10 -------> equation B
x - y - 2z = -2 ------> equation C
In this problem we have that
equation A is the same that equation B
because, if you multiply equation A by 2 obtain equation B
so
we have obly two equations and three variables
4x + y + 5z = 5 -------> equation A
x - y - 2z = -2 ------> equation C
The system can be solved, but there is no unique solution.
so
assume a value of z
I will assume z=0
we have
4x + y = 5 -------> equation A
x - y = -2 ------> equation C
isolate the variable x in the equation C
x=-2+y --------> equation D
substitute equation D in equation A (substitution method )
4(-2+y)+y=5
-8+4y+y=5
5y=5+8
5y=13
y=13/5
Find the value of x
substitute the value of y in equation D
x=-2+13/5
x=3/5