The answer is 900
900/90=10. Therefore 90/900=1/10
        
                    
             
        
        
        
The length of the leg is 5
        
             
        
        
        
(3, -2)
Step-by-step explanation:
y = -2x + 4
-x + 3y = -9
-x + 3 (-2x + 4) = -9
-x + -6x + 12 = -9
-7x = - 9 – 12
-7x = - 21
X = 3
We substitute x with 3 to evaluate y;
-3 + 3y = -9
3y = -6
y = -2
Elimination Method;
y = -2x + 4
-x + 3y = -9
We arrange the equations for substitution;
2x + y = 4
-x + 3y = -9
We multiply the first equation with 3 so we can substract one variable to zero;
3 (2x + y = 4) 
= 6x + 3y = 12
Then we subtract the two;
6x + 3y = 12
-x + 3y = -9
7x = 21
x = 3
We evaluate y by substitution x with 3 in one of the equation;
-x + 3y = -9
-3 + 3y = -9
3y = -6
y = -2
The final answer expressed as a coordinate point is;
(3, -2)
 
        
             
        
        
        
In this case you would set it up as

(180 represents the degree of the triangle)
Add up like terms

Subtract 130 to the other side (180-130)

Divide 10 to the other side ( 50/10)
.

Hope this was clear :)