For what values of a and b will the following system of linear equations has infinitely many solutions ? 21 - 3y = 7 ; (a+b)x - (a +b -3)y = 4a+b​

What kind of bond pays interest which is exempt from tax?

Aswimming pool had 2.5 million liters of water in it. some water evaporated, and then the pool only had 22 million liters of water in it. what percent of the water evaporated?

Sophia wrote an equation to represent the revenue of a movie theater for one day. she let x represent the number of child tickets sold and y represents the nunver of adult tickets sold. if a child ticket cost $4, an adult ticket cost $6, and the total revenue for the daybwas $420, which equation could sophia use to represent the number of chikd and adult tickets that were sold?