Question 7629
5x+y=54  ---->(1) 
4x-y=36  --->(2)

Adding both the equations

5x +y  =  54  
4x -y  =  36  
-----------
9x +0 =  90

we get
9x=90
x=90/9
x=10
now substitute value of x in any of the two equation 
lets plugin the value of x in equation (1)
5(10) +y= 54
50 +y =54
y= 54-50
y=4
 so x=10 and y=4