The total number of years in a century is the same as the number of marbles Gideon has. If he gives 3/4 of the marbles to his sister and multiples the number of remaining marbles by 2, he gets his age five years from now. How old is Gideon now?
A century has 100 years, and if Gideon has as many marbles as the number of years in a century, he has 100 marbles.
If he gives 3/4 of the marbles to his sister, he gives out 3/4*100 = 
<gadget id="calculator">3/4*100</gadget>
<output>75</output>
75 marbles.
Gideon's total number of marbles remaining after giving 3/4 of the marbles to his sister is 100-75=
<gadget id="calculator">100-75</gadget>
<output>25</output>
25.
When he multiplies the number of remaining marbles by 2, he gets his age five years from now, meaning he will be 25*2=
<gadget id="calculator">25*2</gadget>
<output>50</output>
50 years old five years from now.
Currently, Gideon is 50-5 = 
<gadget id="calculator">50-5</gadget>
<output>45</output>
45 years old.

<result>45</result>