Answer:
75 square units
Step-by-step explanation:
(x+10)x=3x^2
x^2+10x=3x^2
10x=2x^2
5x=x^2
x=5
Plugging in 5 into either of the initial equations yields the answer.
 
        
             
        
        
        
It would be 75° because we know it is an acute angle, and an acute angle is an angle less than 90°
        
             
        
        
        
(a). 8x + y = 20, where (b). y = x2 - 2x + 4
So where y is in equation (a), substitute in the value of y in (b). 
8x + (x2 - 2x + 4) = 20
8x + (4) = 20
Get rid of the 4 on both sides (since what you do to one side, you must do to the other)
8x + 4 - 4 = 20 - 4
8x = 16
Get rid of the 8 to leave x on its own
8x ÷ 8 = 16 ÷ 8
x = 2
So now that you have x, find y but substituting in the value you just found (2) into one of the starting equations. 
8x + y = 20 where x is 2.
8(2) + y = 20
16 + y = 20
Minus 16 from both sides
y = 20 - 16 = 4
So x is 2 and y is 4
        
                    
             
        
        
        
Answer:
4m+9
Step-by-step explanation:
4(m+9)
4m+9
4(m+9)=4m+9
 
        
                    
             
        
        
        
<span>m∠CED = 180° − m∠DEB= 90 degrees, by reason corresponding angles of parallel lines are congruent
</span>m∠CFD = 180° − m∠AFD = 90 degrees by reason corresponding angles of parallel lines are congruent