At a bus interchange, 23 more adults than children boarded a bus. When the bus reached Bus Stop Y, 12 adults alighted and 5 children boarded it. When the bus reached Bus Stop Z, only 10 children alighted. In the end, there were 3 times as many adults as children left on the bus.
a) How many children were left on the bus after 10 children alighted from Bus Stop Z?
b) How many adults boarded the bus at the interchange?