X = Dimes Y = Nickels
x + y = 175
.10x + .05y = 13.30
So we know that an average is the sum of the scores divided by the number of scores that were added together. In this case we are going to be dealing with 4 tests. So let's say x is the score for our fourth test. We can create this equation:

So then we need to simplify the top:

Then multiply by 4 on both sides to get rid of the denominator:

Then solve for x:

So now we know that Sam needs to score a 67 on the fourth test to have an average score of 50.
It's 5 because the fraction when you divide. 23.
Answer:
165km ----> 3 hrs
1km --------> (3/165) hrs
440km --------> [(3/165)*440]hr
Answer: 8 hrs