Emily is entering a bicycle race for charity. Her mother play pledges $0.80 for every 0.75 mile she bikes. If emily bikes 12 miles, how much will her mother donate?

Emily bikes 12 miles, generating a donation unit for every 0.75 miles. Her 12 mile ride will generate

12 * 0.75 = 9 donation units. For each of these 9 danation units her mother will donate 80 cents.

It follows that Emily's mom will donate

9 donation units * $0.80 per unit = $7.20.