The length of a city block running north to south in nyc is about 5 times 10 to the negative second power miles. the distance from nyc to mumbai, india is about 7.5 times 10 to the third power miles. the distance from nyc to mumbai is about how many times the length of a nyc north- south block?

So nyc=5 times 10^-2 miles

NYC-Mumbai=7.5 times 10^3

so
5 times 10^-2 times x=7.5 times 10^3
divide both sdies by 5 times 10^-2
x=(7.5 times 10^3)/(5 times 10^-2)
when dividing scientific notation you do this
x=(7.5 times 10^3)/(5 times 10^-2)=(7.5/5) times ((10^3)/(10^-2))
to divide exponents just subtract top from bottom
3-(-2)=5
answer is
x=1.5 times 10^5