1. (2022一下·余杭期中) 口算

12-3=          30+8=            77-7=           6+20=         8+（   ）=15

45-20=            16-7=          99+1=            80-50=           （  ）-5=30

70+5=        82-20=         14-7=           16-8=         42+（  ）=62