I think that inches would be most common for height but centimeters and feet could also be used.
Hi there! :)

6c - (3 - 3c) = 24
Distribute the negative sign with terms inside the parenthesis;
6c - (3) - (-3c) = 24
6c - 3 + 3c = 24
Combine like terms:
9c - 3 = 24
Add 3 to both sides:
9c = 27
Divide both sides by 9:
c = 3.
Answer:
5
Step-by-step explanation:
7+(8-(1+9))
7+(8-10)
7+(-2)
7-2
5