10 / 3t - 11 / (t - 1)
we want the denominators to be the same so:
10(t - 1) / 3t(t - 1) - 11 / (t - 1)
10(t - 1) / 3t(t - 1) - 11(3t) / (t - 1)(3t)
now the denominators are the same, so we can combine the numerators
( 10(t - 1) - 11(3t) ) / 3t(t-1)
( 10t - 10 - 33t ) / 3t(t - 1)
( -23t - 10 ) / 3t(t - 1)