It seems there may be more than meets the eye to this question but in the absence of any further information:

7+7+7 = 21 and can be calculated as a simple addition or as a multiplication seeing as we have three 7s; therefore 3 x 7 = 21.

**Ans: 7+7+7 = 21**

7+7+7

so this is the same as 3*7

but lets work it out so

7+7+7

add the first two sevens together to get 14

14+7

add 7 to 14 to get 21

so the answer would be 21

7 + 7 + 7

First add the first two 7

By adding, your equation would look like

**14 + 7 **now, you should add 14 with 7

By adding 14 with 7, your equation should look like

**= 21 **which is your answer

*This problem is basically 7 X 3 which equals to 21*

7 + 7 + 7 can be done as a simple addition problem or it can be done as thinking of it as a multiplication problem. Multiplication is simply repetitive addition so adding three 7's is the same as multiplying 3 by 7. Either way you look at it, the answer is 21