Composing 30

Probability Level 3

How many ways can the number $30$ be written as an ordered sum of 2s and 5s?

Details and assumptions

There are four ways to write 12 as an ordered sum: $2+2+2+2+2+2=12,$ $2 + 5 + 5 = 12,$ $5 + 2 + 5 = 12$ , and $2 + 5 + 5 = 12$ . The ordered sum can use 0 5's, and it can also use 0 2's.