First you would want to find the length of one eraser and then multiply that by 2. To find the length of one you take the total length or all of them and divide it my the total number of them. 29 1/4 is 117/4.
(117/4) / 13 Dividing by something is the same as multiplying by the opposite.
117/4 × 1/13 = 117/52
Now you multiply by 2.
117/52 * 2/1 Cross simplify
117/26 * 1/1
117/26 inches or 4 1/2 inches.