Answer:
The equal sign (=)
Step-by-step explanation:
It makes sense, the left side is they ride side after subtracting
=
you can spilt 10 9/10 - 1 7/10 into 10-1=9 and 9/10-7/10=2/10 and then add them back together for 9 2/10 which is equal to the other side, 9 2/10
