Answer:
B
Step-by-step explanation:
Hi,
2πr is the formula for circumference, you know your diameter is 4cm and radius is half of the diameter, so your radius is 2cm.
To find the circumference, you have to multiply 2 by 2 and pie. 2 x 2 is 4. So 4 times pie. B is your correct answer.
I hope this helps :)
 
        
             
        
        
        
First set up the equation to find answer: y=7-x. Then add it to the variable. 3x-1(7-x)=1. So that makes it 3x+-7+-1=1. Add like terms -7+-1=-8, so 3x+-8=1. Now to find x just switch the 8 to the other side. So you end up with 3x=9 since when you take away a number from one side you need to use the opposite value so adding 8 to -8 will cancel it out, then add it to the other, then just divide. 9/3=3, from here just substitute to find y. y=7+3. y=10. 
The answer is x=2 and y=5. I hope I helped!
 
        
        
        
Answer:
This is a 30-60-90 triangle so you would do this formula: 
Short side (opposite the 30 degree angle) = x.
Hypotenuse (opposite the 90 degree angle) = 2x.
Long side (opposite the 60 degree angle) = x√3.
Step-by-step explanation:
 
        
             
        
        
        
Answer:
∠ A = 50°
Step-by-step explanation:
The angle adjacent to 145° inside the triangle is
180° - 145° = 35°
The exterior angle of a triangle is equal to the sum of the 2 opposite interior angles.
85° is an exterior angle of the triangle , then
∠ A + 35° = 85 ( subtract 35° from both sides )
∠ A = 50°