X What is the
exchange rate of the
US dollar in
Switzerland when
the exchange rate of
the dollar in Denmark
is 641.40 and the
exchange rate of the
Swiss franc in
Denmark is 656.75?

Explanation:

The first figure has 2 blocks.

The second figure has 4 blocks.

The third figure has 8 blocks

The pattern 2,4,8,... follows the rule "double the current value to get the next one". Because we have this going on, we have an exponential pattern here.

A linear pattern would be something like 2,4,6,8,10,... showing that we add on 2 each time, rather than multiply by 2 each time. So as you can guess, or already know, exponential patterns grow much quicker compared to linear ones.