Question

A collection of coins contains only 10-cent and 5-cent coins.There are x 5cent coins in the collection. Write an algebraic expression for of following.
* The total value of the coins if for every three 10-cent coins there are five 5-cent coins.

Answer 1

I would have defined x as the number of 10cent coins.
By defining the smallest quantity with your variables, usually fractions can be avoided.

But, anyway....

number of 5 cent coins ---- x
number of 10 cent coins ---x/3

value = 5x + 10x/3