To find the answer,we can first calculate how much her sister took away by multiplying the original amount he has to the amount her sister took.
Her sister has:
7/12×2/5
=7/30
We can then find the amount of pizza left by deducting the pizza he has to the answer we found above:
7/12-7/30
=35/60- 14/60
=21/60
=7/20
Therefore he has 7/20 of a pizza left.
An alternative way to find the answer:
7/12×(1-2/5)
=7/12×3/5
=7/20
Hope it helps!
