Find the missing base?!

Find the missing base:

28=34____

does anyone know how to find the missing base?? im lost on how to do this

thanks!

Assuming 28 is in base 10, since 34 base 10 > 28 base 10, use trial and error with bases less than 10.
Try base 9.
3(9) + 4 = 31...no good
Try base 8.
3(8) + 4 = 28...found it. The missing base is 8.