10 tenths = 1 one. Regroup when the tenths sum to 10 or more.

Tenths	=	6 tenths + 7 tenths = 13 tenths
Regroup	=	13 tenths = 1 one + 3 tenths
Ones	=	5 + 4 + 1 (carry) = 10
Sum	=	10.3