Question

keiko has seven colors of lanyard. she uses three different colord to make a keychain. how many different combiantions can she choose?

Answer 1

She can make 12 different combinations.
If she used three different colors for the keychain, there's still 4 other colors left.
4 x 3 = 12

Answer 2

so in order to  answer you´re question i´m going to put every single convination on here right now (as numbers instead of colors from 1 to 7)
123
124
125
126
127
134
135
136
137
145
146
147
156
157
167
234
235
236
237
245
246
247
256
257
267
345
346
347
356
357
367
456
457
467
567
so the answer to you´re question is 36
i hope i helped