Let's break that down:

The word "That" means 
1. "98 miles"

The word "is" means 
2. "equals" 

The words "two fewer than" means 
3. "subtract 2"

The words "four times" means 
4. "multiply by 4"

The question asks for the unknown. So let the number of miles 
that Dave rode be the unknown letter 
5. "x" 

Now to get the equation, start with number 5 and go backwards:

5. x
4. "multiply by 4".  So we have 4x
3. "subtract 2".     So we have 4x-2
2. "equals".         So we have 4x-2 =   
1. "98 miles".       So we have 4x-2 = 98

So the equation is 4x-2 = 98

You can finish now, right?  So I'll stop here.

This demonstrates one trick in getting some word problems to an equation -- 
the trick of 'going backwards'!.

Edwin