Answer:
7 + 8 = 7 + 7 + 1.
Step-by-step explanation:
We know that, 'double plus one facts' is used to make the addition of numbers easy.
For e.g. we have 8 + 9 = 17. This addition can also be done as 8 + 8 + 1 = 17 i.e. we write first term twice and add 1 to get the result.
Hence, we give the name to this type of addition as 'double plus one'.
Now, we have to use this fact for 7 + 7.
So, we consider 7 + 8 = 15.
Therefore, 7 + 8 can be written as 7 + 7 + 1
Hence, the double plus one facts for 7 + 7 is 7 + 8 = 7 + 7 + 1.