Oliver buys yen stamps each costing 77cents
complete the calculation he could do to find the total cost

Hi!
I think that you misspelled the question, and you mean that Oliver bought "ten", not "yen" stamps- yen is the currency of Japan.

So we have 10 stamps of 77 cents each:

10*77=770 cents

He has to pay 770 cents, or since 100 cents are one dollar, 7 dollars and 70 cents.

2) 14.7

3) 50

Step-by-step explanation:

2.

21² = 441

15² = 225

441 - 225 = 216

√216 = 14.69 (rounds to 14.7)

3.

14² + 48² = 2500

√2500 = 50

Pythagoras Theorem lol