Kris had 2 burgers & 1 soda = 770 cal. jack had 3 burgers & 2 sodas = 1260 calories. use 2h+s=770, 3h+s-1260. how many cals are in a burger? soda?
2b + s = 770 ---> s = 770-2b
3b + 2s = 1260
use substitution:
3b + 2(770-2b) = 1260
solve this for b to get burgers
sub back into s = ... to get soda