Answer:
The equation would help determine the cost 1 rubber stamps will be:

Explanation:
Let x be the cost of 11 rubbers.
As the cost of 5 rubber stamps is $9.70.
Thus, the cost of 11 rubbers can be determined using the proportional ratios.

BONUS! let us solve to check

switch sides

Multiply both sides by 11

Simplify

Thus, the cost of 11 rubber stamps: x = $21.34
Therefore, the equation would help determine the cost 1 rubber stamps will be:

VERIFICIATION
Given
The cost of 5 rubber stamps = $9.70
Thus,
The cost of 1 rubber stamps = 9.70 / 5
= $1.94
If the cost of 1 rubber stamp = $1.94
The cost of 11 rubber stamps = 11 × 1.94
= $21.34