When adding 51.2 to a certain number, the sum is 56.05, as seen below. What number should go in the box to complete the addition problem?

Answer:
I know this is already answered but I need points-
two digits to the right you have to carry one, and 1+1+x = 6 so 2+x=6, so x=4
Step-by-step explanation:
Thanks for the points-