Misc: What system is based on the number 60?

Questions

1980s Hits: Paul McCartney and Stevie Wonder sang together on this 1982 hit...?

1980s Hits: The 1984 #1 "Missing You" was sung by this ex-Babys lead singer...?

1980s Hits: The first all-girl group to hit #1?

1980s Hits: This 1985 benefit song hit #1 and was the biggest selling single of the decade?

1980s Hits: This is the only album to ever have five #1s...?