Together, a double cheeseburger and a small order of fries cotains 690 calories. the fries have half as many calories as the double cheeseburger. determine the number of calories in each

X+y=690

y=x/2

x = calories in double cheeseburger

y = calories in fries

set both problems to y then set them equal to each other like so ...

y=690-x

y=x/2

690-x=x/2 times by 2

1380-2x=x Add 2x to other side

1380=3x divid by 3

x=460

To find y plug 460 into y=x/2

y=460/2

y=230

cheeseburgers have 460 calories and fries have 230 calories.