if 57% of the registered voters cast 273,600 votes in an election, how many registered voters are there?

57% of registered voters cast 273,600 votes
let's write the registered voters as x
57% of x = 273,600
57% = 0.57
0.57 * x = 273,600
divide both sides by 0.57
x = 480,000

To check:
57% of 480,000 =?= 273,600
0.57 * 480,000 =?= 273,600
273,600 = 273,600

There are 480,000 registered voters.

Hope this helps