One wheel spins faster than the other

my gpg was easy to assemble but now that i got to coding it appears that one wheel is spinning faster that the other. Don’t know if its a motor problem but when i run the code it fades to the left other than going straight forwards please help because i really enjoy coding and what to show my mom a fully functioning robot.

If the speeds are different on the two wheels, then you can use trim to increase or decrease the speed on one of the wheels and make the GoPiGo move straight. Here are the instructions to do that:

Do let us know if this helps.