This looks like "half" a property. I'm assuming you mean something that looks like this:
IF a + b = a + c, THEN b = c. In the expression in your problem, the role of a is being played by 7. The role of b is played by (4 + 6), and the role of c is played by n.
The conclusion would be that 4 + 6 = n.
But you asked about what the property is called. The likely name is the subtraction property of equality. How did we go from a + b = a + c to the conclusion b = c? We subtracted a from both sides of the equation.
SSS - the side they're sharing is also congruent so if you just add in the other congruent sides you get SSS
For number 1)
you must first split the figure, so subtract the 8 mm from 12 mm to find the width.... = 4mm
so you use the numbers 10 x 2 x 4 = 80 mm
and 2 x 8 x 3 = 48 mm
80 mm + 48 mm = volume of the figure
All you have to do is look it up on line then put answer key at the end of the thing you looking up
The formula for the confidence interval is given by
Sample mean + z*[σ/√n], and
Sample mean - z*[σ/√n]
We have:
Sample mean = 23.95
n = 40
σ = 2.55
z* for 99% confidence = 2.58
Substitute these values into the formula, we have
23.95 + (2.58)(2.55÷√40) = 24.99
23.95 - (2.58)(2.55÷√40) = 22.91
So the lower interval is 22.91 and the highest interval is 24.99