Answer:
B must travel at the rate of 10 miles per hour.
It would be
, or, in simplest form,
.
You get this by adding all the marbles to find the total number of marbles. <em>10+7+12+9</em>, which equals <em>38</em>.
You have <u>10 red marbles out of 38 total</u>, so that is represented by
!
The original expression is given by:

The correct way to rewrite the expression is given by:

For this, we use two properties:
Associative property:
The way of grouping the factors does not change the result of the multiplication:
Commutative property:
The order of the factors does not vary the product:
1) Given
2) Adding segments AB and BC together gives AC (Addition postulate, not too sure about the terminology)
3) Segment Addition postulate
4) Segment Addition postulate(Knowing that AC=BD, the distance between BC and CD add up to BD, shown in #3. AB and BC add together to give AC)
5) Subtraction property of Equality
Hope I helped :)
Are there anymore numbers after the six? If there is not then it si already rounded to the nearest tenth.