Answer:
Nina practiced the viola for 11.25 hours last week.
Step-by-step explanation:
Juan practiced the violin for 9 hours last week. For each 3 hours that he practices the violin, he practices 2.5 hours of cello. So
3h violin - 2.5h cello
9h violin - xh cello


He practiced 7.5 hours of cello, the same as Nina.
For every 3 hours Nina spends practicing the viola she practices the cello for 2 hours. So:
3h viola - 2h cello
xh viola - 7.5h cello



Nina practiced the viola for 11.25 hours last week.
 
        
             
        
        
        
Perimiter=6 times legnth of one side
P=6(x+1/3y)
P=6x+6/3y
P=6x+2y
if x=5 and y=6
P=6(5)+2(6)
P=30+12
P=42
A. P=6x+2y
B. 42 units is the perimiter
        
             
        
        
        
1. Anwser=53.3 (do 40*3 then anwser x 4)
2anwser=120
        
             
        
        
        
X + y + z = 2
x - y + 5z = 6
cancelando +y com -y:
x + z = 2*(-5)
x + 5z = 6
-5x -5z = -10
...x +5z = 6
---------------------
-4x = -4 *(-1)
4x = 4
x = 4/4
x = 1
x + z = 2
1 + z = 2
z = 2 - 1
z = 1
x + y + z = 2
1 + y + 1 = 2
2 + y = 2
y = 2 - 2
y = 0 
S: {x, y, z} = {1, 0, 1}
        
             
        
        
        
Answer:
D. 10 < x < 43
Step-by-step explanation:
4x+8 must be greater than 48, but less than 180.
48 < 4x + 8 < 180
40 < 4x < 172
10 < x < 43