The expression is 
Place value chart for
and 4.2.

| \
\ | \
\
\ | \
\
\ | \
\
9 \ | \
\
4 \ | \
\
\ | \
\
\ | \
| \
\ | \
\
\ | \
\
\ | \
\
4 \ | \
\
2 \ | \
\
\ | \
\
\ | \
\
Line up the decimal points and draw a line below the numbers.
\\

First find the sum of the tenths digit.
\The sum of the tenths digit
.
The sum is 10, so carry digits to the next column on the left
\
Next find the difference of the ones digit.
\The difference of the ones digit =
.

The difference is
.