If 50 jackes have been sold in February and the team will get bonus by selling 30% more jackets in March, then they'll need to sell:
30% * 50 =
= 30/100 * 50 =
= 3/10 * 50 =
= 3 * 5 =
= 15 [more jackets]
So they'll get the bonus after selling 50 + 15 = 65 jackets.