Children explain subtraction is identifying which number we could make a group of that would give us enough to take away the other number, then starting with 1 group, and taking a group away, and investigate subtracting single-digit numbers bridging to 10, using the place value concepts they have been investigating.
As children are investigating adding (and subtracting) bridging 10, they continue to investigate the place value concepts of friends of 10 (Place Value 6), partitioning single-digit and teen numbers (Place Value 8), and place value of teen numbers (Place Value 7).
Children may move seamlessly between investigating adding and subtracting bridging 10 and investigating the place value concept that they are trying to apply.