Question is in picture

Which equation can be used to measure the density of water in a spherical water tank? let w represent the number of water particles within the region.

Atruck can be rented from company a $50 a day plus $0.60 per mile. company b charges $20 a day plus $0.80 per mile to rent the same truck. find the number of miles in a day at which the rental costs for company a and company b are the same

y=2x−1 5x−4y=1 is (1,1)(1,1) a solution of the system?