X-y-2z=4 -x+3y-z=8 -2-y=4z=-1 what is the new 2x2 system

What is the missing reason in the proof? segment addition congruent segments theorem transitive property of equality subtraction property of equality?

There are 93 calories in a small candy bar how many calories are ther in a half dozen small candy bars?

What is the slope of any line parallel to the line 8x+9y=3 in the standard (x,y) coordinate plane?