Answer:
Step-by-step explanation:

15²-9²= x² use Pythagoras' theorum and square the two smaller sides to get the square of the hypotenuse (the diagonal) then rearrange this to get the above calculation
Answer:
3.5x10³
Step-by-step explanation:
7x10^5=700000
2x10^2=200
Divide both by 100
7000÷2=3500
divide by 1000 as standard form is less than 10
1000 is 10 cubed
3500÷1000 is 3.5
∴3.5x10^3 is answer