Answer:
More detail needed
Step-by-step explanation:
The question is not clear, therefor there is no way to solve it.
The sign of the product of -21 and 451 is going to be negative. That is because of the rule when you are multiplying a positive number times a negative number. A positive number times a negative number will always be negative. Here are some helpful rules to know:
positive * positive = positive
negative * positive = negative
negative * negative = positive (the negatives cancel each other out)
Since this question has numbers that fit the second case, the answer will be negative.
The number of sections made is 
<em><u>Solution:</u></em>
Given that, Sarah paints a straight line
The line is
feet
She wants to divide the line into sections that are each 18 ft long
To find: Number of sections
From given,


Number of sections can be found by dividing the total length of line by length of 1 section

Substituting the values, we get,

Thus number of sections made is 