I think addition property of equality
Answer:
Step-by-step explanation:
step 1
Find the measure of the arc DC
we know that
The inscribed angle measures half of the arc comprising
![m\angle DBC=\frac{1}{2}[arc\ DC]](https://tex.z-dn.net/?f=m%5Cangle%20DBC%3D%5Cfrac%7B1%7D%7B2%7D%5Barc%5C%20DC%5D)
substitute the values
![60\°=\frac{1}{2}[arc\ DC]](https://tex.z-dn.net/?f=60%5C%C2%B0%3D%5Cfrac%7B1%7D%7B2%7D%5Barc%5C%20DC%5D)
step 2
Find the measure of arc BC
we know that
----> because the diameter BD divide the circle into two equal parts
step 3
Find the measure of angle BDC
we know that
The inscribed angle measures half of the arc comprising
![m\angle BDC=\frac{1}{2}[arc\ BC]](https://tex.z-dn.net/?f=m%5Cangle%20BDC%3D%5Cfrac%7B1%7D%7B2%7D%5Barc%5C%20BC%5D)
substitute the values
![m\angle BDC=\frac{1}{2}[60\°]](https://tex.z-dn.net/?f=m%5Cangle%20BDC%3D%5Cfrac%7B1%7D%7B2%7D%5B60%5C%C2%B0%5D)
therefore
The triangle DBC is a right triangle ---> 60°-30°-90°
step 4
Find the measure of BC
we know that
In the right triangle DBC
substitute the values
Answer:
n=3
Step-by-step explanation:
Simplifying
8n + 12 + -5n = 21
Reorder the terms:
12 + 8n + -5n = 21
Combine like terms: 8n + -5n = 3n
12 + 3n = 21
Solving
12 + 3n = 21
Solving for variable 'n'.
Move all terms containing n to the left, all other terms to the right.
Add '-12' to each side of the equation.
12 + -12 + 3n = 21 + -12
Combine like terms: 12 + -12 = 0
0 + 3n = 21 + -12
3n = 21 + -12
Combine like terms: 21 + -12 = 9
3n = 9
Divide each side by '3'.
n = 3
Simplifying
n = 3
Answer: Elaine=13 years old Tyler=21 years old
Step-by-step explanation:
Let x = Elaine's age, so her brother Tyler's age = x+8
Elaine+Tyler=34
x+(x+8)=34
2x+8=34
2x=26
x=13
Elaine=13 years old
Tyler=21 years old
