Uri buys two burgers and a soda for $2.10, and Gen buys a burger and two sodas for $2.40 . How many cents does a soda cost?

Let the price of 1 burger =B

Let the price of 1 soda =S

2B + S = $2.10....................(1)

B + 2S = $2.40....................(2)

Now, you have 2 simultaneous equations. Do you think you can solve them? Try it.

Try using substituion method to solve this problem, where you find what S equals in terms of B, then substituting S in the second equation for that.