ANSWER

Step-by-step explanation
Let the number of red ones be r.
Let the number of white ones be w.
Let the number of blue ones be b.
There are 305 M&Ms in the bag. This means that:

There are three times as many red as white. This means that:

The blue are five more than twice the white. This means that:

We can substitute these into the first equation:

Solve for w:

To find how many blue M&Ms are there, substitute the value of w into the equation for b:

That is the number of blue M&Ms in the package.