Irrational because it’s not a perfect square.
        
             
        
        
        
9*12=108
4*x=4x
so,  4x/108
4x=108
x=27
        
                    
             
        
        
        
Step-by-step explanation:
his father's age= 4x
his mother's age= 4x- 7
his age= x
x+4x+4x-7=101 
x+ 4x+ 4x= 101+ 7
9x= 108
 =
= 
x= 12
Tesfa is 12 years old
 
        
                    
             
        
        
        
You should start with an equation.

The 'x' represents the week.
so now, we have to subtract 125 from the total amount which is 245.

now we have 

to find 'x', we must divide 15 on each side 

we are now left with 

that means Sierra will have 8 weeks until she has enough money to buy the bike
 
        
        
        
Answer:
a=2.48
c=9.52
Step-by-step explanation:
a+c=12
4a+7.5c=72.5 Given
a+c=12
-4a-7.5c=-72.5 multiply the equation by negative 1
-3a-6.5c=-60.5 simplify
-3a=-60.5+6.5c add 6.5c to both sides
a=-20.17+2.17c divide it by 3
now you would take that equation and plug it into an equation you already have since you have something to plug in for a, the easiest one to do is a+c=12
(-20.17+2.17c)+c=12 plug in the equation
-20.17+3.17c=12 simplify by solving for c
3.17c=30.17 add 20.17 to both sides
c=9.52 divide both sides by 3.17
now since you have found c, you can plug it in to you equation to solve for a now (use the ones from the second step).  I am using the equation a+c=12.
a+9.52=12 plug in the variable and solve for a
a=2.48 subtract 9.52 to both sides
a=2.48
c=9.52