[Using 400 and 285 in these examples.]
a. 400 / 285 = 1.4035. Subtract the 1 and multiply by 100. Seattle's sales are 40.35% larger than Portland's.
b. 285 / 400 = 0.7125, so Portland's sales are 71.25% of Seattle's. 100 - 71.25 = 28.75, so Portland's sales are 28.75% less than Seattle's.
c. 285 / 400 = 0.7125, so Portland's sales are 71.25% of Seattle's.