Answer:
Echo can plant a maximum of 8 shrubs.
The total cost for Echo's shrubs is = 8 
 $15.32 = $122.56
 $15.32 = $122.56
Explanation:
i) Garden is 36 feet wide
ii) Each shrub is 4.5 feet wide.
iii) therefore the maximum number of shrubs that can be planted are 

 Therefore Echo can plant a maximum of 8 shrubs.
Therefore the total cost for Echo's shrubs is = 8 
 $15.32 = $122.56
 $15.32 = $122.56