Do the FOIL method. (F)irst, (O)uter, (I)nner, (Last, In Which you multiply the first set of number and variables in each set, (3s times 3s), the outer set of number and variable in each set, (3s times negative 3t, the inner number and variable in each set,(2t times 3s), and the last ones, (2t times negative 3t).
