Question

Penny and Kenny have the same number of football cards.

Answer 1

Hello,
Penny==>a*10 (a is an integer)
Kenny==>b*18 (b is an integer)

a*10=b*18==>a=9*b/5 ==>b=5+n*5
a=9*(5+5*n)/5=9*(1+n)=9+9n
If n=0 then a=9 and b=5 :Number od cards: 9*10=10, 5*18=90
if n=1 then a=19 and b=10: Number of cards: 19*10=190>100 to exclude.

So number of cards=90