Answer:
The guinea pig is 210 mm longer than Naomi's fish
or
The guinea pig is 21 cm longer than Naomi's fish
Step-by-step explanation:
Remember that
1 cm=10 mm
<u><em>Convert cm to mm</em></u>
guinea pig ------> 25 cm=25*10=250 mm
Subtract the length of Naomi's fish from the length of her guinea pig
so
250-40=210 mm
<u><em>Convert to cm</em></u>
210 mm=210/10=21 cm