7. media= 32.4+8.16=40.56 aprox=40.6
8. a=0.72(405)
S=7+2+33×4+33×0+32×5=
=7+2+132+160=
=301
9. a,b+b,a+a+b=10.5
a,b=ab/10
b,a=ba/10
ab/10+ba/10+10a/10+10b/10=105/10
ab+ba+10a+10b=105
10a+b+10b+a+10a+10b=105
21a+21b=105
21(a+b)=105
a+b=5
a=1 b=4 ab=14
a=2 b=3 ab=23
a=3 b=2 ab=32
a=4 b=1 ab=41
a=5 b=0 ab=50
S=14+23+32+41+50=160