Resolución de problemas mediante sistemas de ecuaciones.

plantear un problema, cuya expresión algebraica coincida para cada uno de los siguientes sistemas de ecuaciones, no debe resolver el sistema de ecuaciones.
a. x +y = 13 b. 3x - 30y = 15 c. 8x+3y=37 d. x-5y=4
x-y=1 2x + 10y = 40 8x-3y=50 3x+5y=32

Using elimination, what is -4x+2y=-12 4x+8y=-24

Luke started a weight-loss program. the first week, he lost x pounds. the second week, he lost pounds less than times the pounds he lost the first week. the third week, he lost 1 pound more than of the pounds he lost the first week. liam started a weight-loss program when luke did. the first week, he lost 1 pound less than times the pounds luke lost the first week. the second week, he lost 4 pounds less than times the pounds luke lost the first week. the third week, he lost pound more than times the pounds luke lost the first week.

Tommy buys a sweater that is on sale for 40% off the original price. the expression p -0.4p can be used to find the sale price of the sweater, where p is the original price of the sweater. if the original price of the sweater is 50, what is the sale price?