1) =2³/3³=8/9
2) =3³/2³=9/8=2 1/8
1)120+40=160
2)160-70=90
3)90-57=33
<span>1)-0,7x=343
x=</span>343:(-0.7)<span>
x=-490
</span><span>2)0,81x-71=1,11x+1
0.81x-1.11x=71+1
-0.3x=72
x=72:(-0.3)
x=-240</span>
S=(V1-V2)t => t=S÷(V1-V2) = 60÷(15-12) = 20 часов