I am confused ;-; pls help

Can someone tell me if this is perpendicular? !

X+ 4y − z = −14 5x + 6y + 3z = 4 −2x + 7y + 2z = −17

Chuck is making a salad to go with his soup. the recipe calls for 2.1 cups of lettuce per person and 0.56 ounces of salad dressing per cup of lettuce. if 11 dinner guests want salad, how many ounces of dressing will be necessary? round the answer to the nearest whole ounce. 1 ounce 2 ounces 6 ounces 13 ounces