Read this and answer the question

Labour improved its performance in 1987, gaining 20 seats and so reducing the Conservative majority from 143 to 102. They were now firmly re-established as the second political party in Britain as the Alliance had once again failed to make a breakthrough with seats. A merger of the SDP and Liberals formed the Liberal Democrats. Following the 1987 election, the National Executive Committee resumed disciplinary action against members of Militant, who remained in the party, leading to further expulsions of their activists and the two MPs who supported the group.

How many more seats did LAbour get in 1987?
20