Respuesta :
					                   the first one is 21 12 times 3 is 36 minus 3 times 5 is 15 36 minus 15 is 21 
Next one 4 times 3 is 12 minus 5 is 7
12x-3y=21
4x-y=7
					                
					             Next one 4 times 3 is 12 minus 5 is 7
12x-3y=21
4x-y=7
 
			                   
					                  