If the '7t' is supposed to be '7y', then the answer is below
(4y+8)-(7y-12)=11
distribute the negative into the second parenthesis
4y+8-7y+12=11
combine like terms
-3y+20=11
subtract the 20 from both sides
-3y=-9
divide by -3 on both sides
y=3
if it is supposed to be '7t', I'm not sure if there's enough information
Answer: 21.3 km
Step-by-step explanation:
Given: On each of 3 days the distance traveled by Derrick to school = 6.45 km
The distance rode by Derrick to library = 150 meters
Since, 1 m=
Thus, the distance rode by Derrick to library = 
The distance rode by Derrick to home = 500 meters.
Thus, the distance rode by Derrick to home = 
Distance he rode in each day = 
Now, Distance he rode in 3 days = 
11.2 * .05 = .56
sales tax = .56
11.2+.56 = 11.76
groceries plus tax = 11.76