(a:3+16)*2=40
a:3+16=40:2=20
a:3=20-16=4
a=4*3=12
2. a:4=c rest r, c=r, a:4=r rest r, a= 4*r+r,
r∈{0,1,2,3}
a=4*0+0=0
a=4*1+1=4+1=5
a=4*2+2=8+2=10
a=4*3+3=12+3=15
3. a:6=c rest r, c=2r, a=6*2r+r=13r
r∈{0,1,2,3,4,5}
a=13*0=0
a=13*1=13
a=13*2=26
a=13*3=39
a=13*4=52
a=13*5=65
4.a:5=12 rest r, r∈{1,3}
a=5*12+r=60+r
a=60+1=61
a=60+3=63