Question

Lin and Jen each thought of a number. Lin thought of a 2-digit number. Jen’s number is 7 times as big as Lin’s. But, if Lin writes 0 between the digits of her number, she’ll get Jen’s number. What are the numbers?

Answer 1

The numbers are 15 and 105.

Lin thought a two digit number that is 15, if we multiply 15 with 7 , 15 x 7 = 105 that is we get Jen's number.
and if we put 0 between the two digits of Lin's number, we also get Jen's number;
that is 105.