To combine these terms you would add up the a's and b's.
4a+b+a is the same as 4a+a+b. Anything without a constant in front has a value of 1. You have 4a's and you need to add another a. That equals 5a's. The b is left alone since you can only add like variables.
The answer would be C) 5a +b
<span>The two checkpoints are 4,920 ft. apart from each other. The total distance of the race is 15,840 ft. If checkpoint C half the distance between checkpoint B and the end of the race, the distance between Checkpoint B and the end of the race is 9,840 ft. Half of that distance is 4,920 ft.</span>
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