1. 1м=100см.
3дм=30см
V=40×100×30=120 000см^3=120дм^3
320:(52-х)=8
52-х=320:8
52-х=40
х=52-40
х=12
проверка
320:(52-12)=8
320:40=8
8=8
3 - 2 5/9 = 1 - 5/9 = 9/9 - 5/9 = 4/9
<span>(2_8/9+ 1_7/15)*(1/7+8/49)=
</span><span>2_8/9+ 1_7/15= 3_40/45+21/45=3_61/45=4_16/45
</span><span>1/7+8/49=7/49+8/49=15/49
</span>4_16/45*15/49=196/45*15/49=4/3=1_ 1/3