Write down multiples of each number until you find the first common multiple:

The multipliers of 56 are: 56, 112, 168, 224, 280, 336, 392, 448, 504, 560, 616, 672, 728, 784, 840, 896, 952, 1008, 1064, 1120, 1176, 1232, 1288, 1344, 1400, 1456, 1512, 1568, 1624, 1680, 1736, 1792, 1848, 1904, 1960, 2016, 2072, 2128, 2184, 2240, 2296, 2352, 2408, 2464, 2520, 2576, 2632, 2688, 2744, 2800, 2856, 2912, 2968, 3024, 3080, 3136, 3192, 3248, . . .

The multipliers of 84 are: 84, 168, 252, 336, 420, 504, 588, 672, 756, 840, 924, 1008, 1092, 1176, 1260, 1344, 1428, 1512, 1596, 1680, 1764, 1848, 1932, 2016, 2100, 2184, 2268, 2352, 2436, 2520, 2604, 2688, 2772, 2856, 2940, 3024, 3108, 3192, 3276, . . .

The multipliers of 133 are: 133, 266, 399, 532, 665, 798, 931, 1064, 1197, 1330, 1463, 1596, 1729, 1862, 1995, 2128, 2261, 2394, 2527, 2660, 2793, 2926, 3059, 3192, 3325, . . .

We can see that:

LCM( 56, 84, 133 ) = 3192

This solution can be visualized using a Venn diagram.

The LCM is equal to the product of all the numbers on the diagram.