-7x -7y = 21
Y = 6
Since they are giving you the value of 6 you just plug it in the equation
-7x - 7(6) = 21
-7x - 42 = 21
+ 42. +42
-7x = 63
/-7. /-7
X = -9
Problem 1
The error is 2 inches since her estimate is 2 inches off the true value.
We can think of it like this
4 feet = 4*12 = 48 inches
4 feet, 2 inches = 4 ft + 2 in = 48 in + 2 in = 50 inches
So she guesses he is 48 inches, but he's really 50 inches, so 50-48 = 2 inches is her error.
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Problem 2
Divide the error (2 inches) over the actual height (50 inches) to get
2/50 = 4/100 = 4%
The percentage error is 4%
This means she is 4% off the target.
Note how 4% of 50 = 0.04*50 = 2 which was the error we found back in problem 1.
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