To find the amount \( a \) that Mike paid for buying 8 yards of ribbon, we first need to calculate the total cost of the ribbon. The cost per yard is $3.50, and he bought 8 yards.
The equation to represent the total cost \( a \) can be set up as follows:
\[ a = \text{cost per yard} \times \text{number of yards} \] \[ a = 3.50 \times 8 \] Calculating this gives:
\[ a = 28 \]
So, Mike paid $28 for the ribbon.
If you want to express this as \( \frac{a}{8} \):
\[ \frac{a}{8} = \frac{28}{8} \]
Thus, we can complete the equation:
\[ \frac{a}{8} = 3.50 \]
So the final working equation is: \[ \frac{a}{8} = 3.50 \]