Binomial distribution

If n = 7, how many ways are there of getting 3 successes?

1: 123
2: 124
3: 125
4: 126
5: 127
6: 134
7: 135
8: 136
9: 137
10: 145
11: 146
12: 147
13: 156
14: 157
15: 167
16: 234
17: 235
18: 236
19: 237
20: 245
21: 246
22: 247
23: 256
24: 257
25: 267
26: 345
27: 346
28: 347
29: 356
30: 357
31: 367
32: 456
33: 457
34: 467
35: 567