Define variables and write an equation,

Question

William bought tickets for a concert. The adult tickets cost $30 per ticket, and the children’s tickets cost $20 per ticket. If he spent a total of $270, then how many of each ticket did he buy?

Answer 1

30 a + 20 c = 270

You need more information because you need two equations to solve for two variables. For example you might say there were 10 more children than adults c = a + 10 but the problem did not give you anything like that so you can write one equation but not solve the problem.