How to subtract this question 91.49-0.7

We can start by leaving the 9 in the hundreths place alone as this is not affected. We can then subtract 7 from 4 for the tenths place. This gives - 3. As this is a negative number, we need to subtract 1 from the next place (the units) and then take another 3 from the tenths place. This gives us an answer of 90.79 (where both the 9's are unaffected).