21. if Sam's erasers are represented by x, then sari, who has three times more, would be represented by 3x. since you are adding two together to get 28, the equation would be 28=3x+x. Simplify to 28=4x, divide by 4 to isolate x, where x=7. multiply this by 3 to get sari's amount.
The side AB measures option 2.
units long.
Step-by-step explanation:
Step 1:
The coordinates of the given triangle ABC are A (4, 5), B (2, 1), and C (4, 1).
The sides of the triangle are AB, BC, and CA. We need to determine the length of AB.
To calculate the distance between two points, we use the formula 
where (
) are the coordinates of the first point and (
) are the coordinates of the second point.
Step 2:
For A (4, 5) and B (2, 1), (
) = (4, 5) and (
) = (2, 1). Substituting these values in the distance formula, we get

So the side AB measures
units long which is the second option.