There follows the formula for "z-score:"
raw score - mean
z = ------------------------------
standard dev
9.1 - 8
Here, the z-score is z = ------------- = 0.344
3.2
X= weight of TV
y= weight of CD
3x+5y= 62.5
3x+ 2y= 52
You can either solve for a variable, or eliminate a variable by subtracting the second equation from the first:
3x + 5y = 62.5
-(3x+2y = 52)
0 + 3y = 10.5, so y = 10.5/3 or 3.5.
Now plug y= 3.5 back into any equation to get x:
3x + 5(3.5) = 62.5
3x + 17.5 = 62.5
3x = 45
x = 15
Always check work. Both equations should be true for x=15, y= 3.5
X + y = 10
x - y = 2
add the equations together
2x = 12
x = 6
6 + y = 10
y = 3
Simplify 2/3 - 1/7 to 11/21
10/21 + 11/21
Simplify
The answer is 1.
