How do I work a problem like this?

5/8 + m = 1

1-5/8

to get variable 'm' alone, transpose all terms not containing m to the right side of equation,, but remember to reverse the sign:

5/8 + m = 1
m = 1 - 5/8
*note that the sign of 5/8 becomes negative*
then to subtract fractions, you need to convert 1 to a fraction such that its denominator is equal to 8:
1 = 8/8
now,
m = 8/8 - 5/8
m = (8-5)/8 = ?
now, solve for m. :)