What is 8 21/40 i don't understand how to do it

Hey, there !

If you want to know it as a "improper fraction" , you can

Multiply the denominator from the front number
Whatever the denominator and front number is , you add it to the numerator

So, for this problem we first have the multiply the front number from the denominator

Like: 8 (40)
That gives us the answer of: 320

Now we have to add 320 to 21

Like: 320 + 21

That gives us the answer of:341

We keep our denominator (which is "40" )

Your improper fraction would be:

341 / 40

Good luck on your assignment and enjoy your day!

~MeIsKaitlyn:)