Substitue y=3x into the other equation to get 3x=-x+4. Solve this to get 4x=4 therefore x=1.
knowing this, y=3
The rule of scientifinc notation is that we can use number between 0 and 10, so here we can use 2.8. Lets do this
280 000 000 = 2.8 * 100 * 1 000 000
Now we can just multiply 2.8 by 10 to the power of number of 0 reapeted
So

- its the result
You never gave a question therefore there is no answer without a question