Answer:
-37/5= y 
x=11/5
Step-by-step explanation:
4x-3y=31
-3y=-4x+31 regroup it to match the other 
 -2 y=(2x-3)(-2) multiply by -2 to get -4x
-3y=-4x+31
-2y=-4x+6 adding 
-5y=37 divide 
-37/5= y 
4x-3(-37/5)=31
x=11/5
 
        
             
        
        
        
150 miles= in 3 hours
150 miles/3 hours 
= 50mph