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.
Area formula: pi * radius * radius
Radius=1/2diameter=1/2(7)=3.5
3.5*3.5*pi=12.25pi square feet
Circumference formula: pi * diameter
7*pi=7pi feet
1.5% of 4,000$ is 60$ . 60$ times 3 years = 180$
Answer:
t represents the time in minutes since the balloon started descending.
a(t) represents the altitude of the balloon at t minutes.
a(5.5) gives the altitude at 5.5 minutes.