What is the rate of change for the liner relationship modeled in the table?

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The party planning committee has to determine the number of tables needed for an upcoming event. if a square table can fit 8 people and a round table can fit 6 people, the equation 150 = 8x + 6y represents the number of each type of table needed for 150 people.

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.