[tex](a \times 2 - 40) \div 8 = 12 \\ a \times 2 - 40 = 12 \times 8 = 96 \\ a \times 2 = 96 + 40 = 136 \\ a = 136 \div 2 = 68[/tex]
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Al doilea:
[(a-1):100+90]:10-10=0
[(a-1):100+90]:10=10
(a-1):100+90=10×10=100
(a-1):100=100-90=10
a-1=10×100=1000
a=1+1000
a=1001
