Explicație pas cu pas:
a)
Restul <30=>câtul<30
a:30= 1 rest 1=> a-1=30=>a=31
a:30= 2 rest 2=>a-2=30×2=>a=62
a:30=3 rest 3=>a=93
a:30=4 rest4=>a=124
.....
a:30= 29 rest 29=>a-29=30×29=>899
b) a:30=c+rest ;rest<30
a:30=2rest+rest
a:30=2 rest 1=>a-1=30×2=>a=61
a:30=4 rest 2=>a-2=30×4=>a=122
.....
a:30=28 rest 14=>a-14=30×28=>a=854
c) a:30=c+rest
a:30=1/2rest+rest
a:30=1 rest 2=>a-2=30×1=>a=32
a:30=2 rest 4=>a-4=30×2=>a=64
a:30=3 rest 6=>a-6=30×3=>a=96
.....
a:30= 14 rest 28=>a-28=30×14=>a=448