Answer:
25
Step-by-step explanation:
The distance is the magnitude of the difference:
|(2 -3i) -(9 +21i)| = |-7 +24i| = √((-7)² +24²) = √625 = 25
The distance between the two points in the complex plane is 25 units.
Answer: (-3,3) is the answer
Consider this option:
1. if to re-write the condition, it is given: total time t=8 hours; upstream=downstream=6 miles; V_boat=4 m/h., V_current=V=?
2. note, that total time=time_upstream+time_downstream, where time_upstream=6miles/(V_boat-V) and time_downstream=6miles/(V_boat+V). Using this it is possible to make up and solve the following equation:

answer: √10
P.S. the roots of the equation are √10 and (-√10), only positive values is needed for V.
Firstly, you do 90 - 42 to get the amount of brownies sold, which is 48. Then, you put 42 and 48 into a ratio like 42:48. After that, all you need to do is simplify to get 7:8.