Răspuns :
(7×2² +7² × 2³):21
=
=7(2² +7 × 2³):(7×3) =
=(2² +7 × 2³):3 =
=2²×(1 +7 × 2):3=
=2²×15:3=
=2²×5=20
=7(2² +7 × 2³):(7×3) =
=(2² +7 × 2³):3 =
=2²×(1 +7 × 2):3=
=2²×15:3=
=2²×5=20