Which expression gives the z-coordinate of the solution of the system x+2y-2z=3?

From the system of equation
x+2y-2z=3
3x-y+z=16
x+z=7
we solve the system as follows:
add equation i and ii
x+2y-2z=3
6x-2y+2z=32

7x=35
x=5
thus
z=2

2y+5-4=3
2y=2
y=1

hence
x=5, y=1 z=2

1. 0.3 •4 is the same as 4 groups of 0.32. 7•0.8 is the same as 7 groups of 0.83. it increases by 0.5 every time, so 0.5x4 it increases by 0.9 every time, so 0.9x5. 0.9•12=10.86. 0.47•5=2.35i can finish the next ones in a separate post