Answer to Problem # 11:

 6 Y + 3Z = 30     and      Z = 3Y    
 6Y  +  3 (3Y)  =  30         6Y + 9Y = 30

	 15Y = 30      Y = 2 (ANSWER)    and  
 	Z =   3Y   =   3 x 2     Z = 6 (ANSWER)


return