Răspuns:
a) 70-4=66
30-6=26
90-1=89
50-5=55
a) 70-4=35+35-4
30-6=15+15-6
90-1=45+45-1
50-5=25+25-5
b) 20-3=10+10-3
80-7=40+40-7
40-2=20+20-2
60-8=30+30-8
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