Hey there! I'm happy to help!
Like terms are numbers with the same variable and same power. 5 and 7 are like terms because they have no variable. 6x and 6y are not because they have different variables. 7x² and 6y² are also not like terms because they have different variables. 7x and 5x are like terms, and 5y³ and 9y³ are like terms.
We see that 2x and -x have the same variables. We can then combine them.
2x-x=x
Now we have x+3=7.
We subtract 3 from both sides, giving us x=4.
Have a wonderful day! :D
