x = 5n + 7
y = n^2
C = {x<30}
D = {30
5n+7<30
n=0 5•0+7<30, x=7
n=1 5•1+7<30, x=12
n=2 5•2+7<30, x=17
n=3 5•3+7<30, x=22
n=4 5•4+7<30, x=27
y=n^2
y=0^2=0
y=1^2=1
y=2^2=4
y=3^2=9
y=4^2=16
C={7,12,17,22,27}
n=6, y=36
n=7, y=49
n=8, y=64
n=9, y=81
D={36,49,64,81}
