To find the amount \( a \) that Mike paid for buying 8 yards of ribbon, we start by determining the equation based on the cost per yard and the total yards he purchased.
The equation can be set up as follows:
\[ a = \text{(cost per yard)} \times \text{(number of yards)} \]
Given:
- Cost per yard = $3.50
- Number of yards = 8
So, the equation is:
\[ a = 3.50 \times 8 \]
Now, let's calculate it:
\[ a = 3.50 \times 8 = 28 \]
Thus, the final answers are:
\[ \frac{a}{8} = 3.50 \quad \text{and} \quad a = 28 , \text{dollars} \]