#2 is a problem on proportions. To start, you should write
(64/36) = (x/45)
I have made it so foreign currency is in the numerator and non-foreign is in the denominator but you can reverse this.
Anyways, then you would cross multiply:
64•45= 36x
2880 = 36x
80 = x
This means that there are 80 foreign coins for a grand total of 125 coins in the box.
