if you have $32 and you want to buy as many train tickets as possible, you could just mentally divide $32 by $4, which is 8 tickets. if the question is asking for an equation, you could create a quick one-step:
4x = 32
so, 4 dollars multiplied by x, the number of tickets, equals 32. then, again, divide 32 by 4 and see that you can buy 8 tickets.