Answer:
187
Explanation:
I personally just do multiplication whenever I can, but that's just me. Like for example I know 100 x 3 = 300 and 200 x 3 = 600. SO it has to be between 100 and 200.
150 x 3 = 450. So know it narrows it down to between 150 and 200.
175 x 3 = 525
180 x 3 = 540
185 x 3 = 555
190 x 3 =570
So now it's between 185 and 190.
Now I just need to do the following.
186 x 3 = 558
187 x 3 = 561
And there we have the answer.